2391 sample questions

2391 exam preperation

2011-07-13T03:22:00.000-07:00

This Section is highlight the areas covered by the 2391 syllabus. Student are expected to
have knowledge of all that is in the syllabus.
Requirements for the Level 3 Level 3 Certificate in the Certification of Electrical
Installations (inspection, testing and certification of electrical installations) (2391-10)
For this qualification, candidates will be required to complete the following assessments:
A written assessment covering outcomes 1-3
A practical assessment
It will be graded pass or fail.
Duration: 2.5 hours
No of questions: 26
This written paper is in two sections. Section A consists of 20 short answer questions
worth 60 marks (1 hour approximately). Section B will consists of 6 structured questions
worth 90 marks (1.5 hours approximately).
Here is the Break down of the examination content.
Section Outcome Unit Title Number of
items
Approximate
percentage %
1 Preparation for
inspection
and testing
3 6
Section A 2 Inspection 2 4
3 Testing 15 30
1 Preparation for
inspection
and testing
Section B 2 Inspection 6 60
3 Testing
Total 26 100

Technical knowledge of the inspection, testing and certification of electrical
installations
The aim of this unit is to enable the candidate to develop the necessary technical
knowledge and understanding about the inspection, testing and certification of electrical
installations.
It is recommended that 15 hours should be allocated for this unit. This may be on a full
time or part time basis.
This unit will be assessed by written examination.
Learning Areas
There are three areas to this unit. These include a knowledge and understanding of:-
Preparation for inspection and testing
Inspection
Testing
Preparation for inspection and testing
The candidate will be able to:
State the need for and the purpose of initial verification and periodic inspection and testing
State the information required to correctly conduct the inspection and testing of an
installation
State the statutory and non-statutory requirements and relevant guidance material that
apply to the activity of inspecting and testing of electrical installations
State the need to comply with statutory and non-statutory requirements, and guidance
material for particular locations and environments in which electrical installations are
installed
State the information to be contained on Certificates and Inspection Reports and how the
information is recorded on all certificates as indicated in BS 7671 (current edition).

Inspection
The candidate will be able to:
State the human senses that may need to be employed during the inspection of an
installation
Refer to and identify the items to be checked during the inspection process for given
systems and locations as detailed in BS 7671 (current edition)
State the particular requirements for a periodic inspection of an electrical installation as
defined in BS 7671 (current edition)
State the need to establish the extent and limitation of a Periodic Inspection Report, with
the client and any relevant third parties, prior to commencing the inspection, and the need
to record these details on the Periodic Inspection Report.
State the requirements of the Electricity at Work Regulations for safe inspection and
testing in terms of those
carrying out the work
using the installation and the building during the inspection and testing.
Testing
For each topic the candidate will be able to:
Instruments
State the need for instruments to be regularly checked and the need for their compliance
with the requirements of BS 7671 (current edition) and HSE Guidance Note GS 38
List the correct instruments, their characteristics and the appropriate scale to carry out
each test and explain the reasons for each choice
State the recommended sequence of tests and the reasons for that sequence
Protective Conductors
State the requirements which need to be considered for protective conductors in terms of
a) earthing conductors
b) main protective bonding conductors
c) supplementary protective bonding conductors
d) circuit protective conductors

Describe the need for, and methods of verifying, the continuity of protective conductors
and the interpretation of results
State the relationship between conductor length, CSA and resistance
State the effect of temperature on a conductor
Ring Circuits
State the effect on measured resistance when cables are connected in parallel
Describe the need for, and methods of, verifying the continuity of ring final circuit
conductors and the interpretation of results
Insulation Resistance
Explain, by example, the effect on insulation resistance and test results of
a) cables connected in parallel
b) variation in cable length
Compare the differences between measurements taken for insulation resistance and
conductor resistance, stating the order of magnitude that would be expected in each case
State the preconditions required for the performance of insulation testing
State the precautions to be taken before testing insulation resistance
Describe methods of testing insulation resistance
State the required test voltages and minimum values of insulation resistance for
installations operating at various voltages
State the particular requirements for insulation resistance testing of circuits incorporating
surge protection devices (SPDs) or sensitive electronic devices, to include disconnection
and the test voltage to be applied where disconnection cannot be achieved.
Electrical separation/SELV
Describe the tests to verify the separation of SELV circuits
State the particular requirements for protection by electrical separation (NOT SELV)

Special Installations and Locations
Describe the requirements for circuits in prescribed special installations and locations, by:
a) identifying the installations and locations to which special requirements apply
b) demonstrating the ability to make reference to the appropriate requirements in each
case
c) identifying the requirements in relation to specific areas and installations from given
information.
IP Code
State the appropriate minimum degree of protection required for given applications as
identified within the IP classification BS EN 60529
Polarity
Describe the need for and methods of testing used to identify correct polarity
Earth Electrodes
Differentiate between the requirements for testing of earth electrodes for RCD protected
TT systems and electrodes for transformers and generators
Earth Fault Loop Impedance
Describe the earth fault loop impedance paths for the following systems
a) TN-S
b) TN-C-S
c) TT
Describe methods of determining earth fault loop impedance in terms of
a) the tests used for measuring actual earth fault loop impedance
b) methods of calculation of earth fault loop impedance from given data and
measurement of conductor impedance
Given maximum tabulated values of earth fault loop impedance, verify that measured
values are acceptable, taking into account conductor operating and ambient temperatures.

Residual Current Devices (RCCBs/RCBOs)
Describe methods of testing the correct operation of RCDs, independent of in-built test
facilities.
State the applications for various RCD ratings
Prospective Fault Current
Describe methods of determining prospective fault current in terms of
a) prospective short circuit current
b) prospective earth fault current
Explain the importance of selecting protective devices appropriate to the prospective fault
current.
Phase Sequence
Describes the requirements for checking phase sequence in terms of
a) the purpose of checking correct phase sequence
b) test methods used to check phase rotation
Voltage Drop
Describe the methods of verifying voltage drop compliance with BS 7671 in terms of
measuring circuit impedance and calculation.

Practical application of the inspection, testing and certification of electrical
installations
The aim of this unit is to enable the candidate to develop the necessary technical practical
skills about the inspection, testing and certification of electrical installations. Demonstrate a
practical application of the testing inspection, testing and certification of electrical
installations
It is recommended that 15 hours should be allocated for this unit.
Practical Activities
The candidate will be able to:
Select the correct instruments or settings and appropriate scales or ranges to carry out
tests
Check and prove instruments and leads for safety and function
Given the information required carry out the inspection and testing of an installation to the
requirements of BS 7671
Complete a Periodic Inspection report, as given in BS7671, including two Schedules of
Test Results
Carry out an inspection of installation components and record deviations and complete a
Schedule of Inspections
The test rig and inspection and testing equipment
To carry out these inspection and testing practical assessments, simulated installations
should be constructed in accordance with the diagrams given in the Assessment Guide for
Centres.
The test rigs should be located in an area of adequate space and light. All connections
must be directly to the accessories, rather than simulated, and allowance should be made
for the replacement of connections as they become worn.
The test equipment provided by the centre must meet the requirements of BS 7671 and
HSE document GS 38.
To ensure that the candidate has to make a selection from the equipment provided, there
should be a greater range of test instruments available than is actually required to carry
out the tests.
The test instruments for Assessment 4 must include a voltage indicator, with the
necessary proving equipment, to test for correct isolation.

To simulate ‘real’ conditions the test rig must be connected to a 400V three-phase and
neutral supply.
Test procedure
The candidate should be given
a. the appropriate results sheet for the assessment
b. a selection of hand tools where required, to carry out the test of the installation
c. a range of test instruments including those required to complete the tests.
Candidate identification and other relevant information should be completed on the
appropriate result sheet prior to the commencement of each test.
The candidate will be expected to record all relevant information and test results for all
circuits on the appropriate results sheet.
The tests and performance assessment
Consideration should be given to the Electricity at Work Regulations throughout the
assessment process, and it should be made clear to the candidate that failure to observe
appropriate safe working practices will result in the assessment being stopped.

2391 questions sample 2

2011-07-13T02:58:00.000-07:00

City and Guilds 2391 Sample Paper A
Page 1 of 6
This examination consists of two sections.
Section A - Twenty short answer questions worth three marks each. Candidates must answer ALL
TWENTY questions. It is recommended that candidates allow approximately one hour for this
section.
Section B—Six structured questions worth 15 marks each. Candidates must answer ALL SIX
questions. It is recommended that candidates allow approximately 11/2 hours for this section.
Section A - Answer ALL TWENTY questions in this section.
1 Three single sockets have been added to a ring final circuit. State the.
a) inspection and test certificate that will need to be completed (1 mark)
b) title in law given to the inspector (1 mark)
c) legal status of the inspector (1 mark)
2 An engineering works is 18 years old and is due for inspection and test.
State the
a) type of inspection and test required (1 mark)
b) documents that must accompany the completed certificate (1 mark)
c) circumstances under which the type of inspection and test in a) above
may not be required.
(1 mark)
3 State the legal status of the following
a) BS 7671 2001 (1 mark)
b) Guidance Note 3 (1 mark)
c) HSE GS38 (1 mark)
4 Give ONE example of EACH of the following
a) an exposed conductive part (1 mark)
b) an extraneous conductive part (1 mark)
c) direct contact (1 mark)
5 State THREE methods of protection against indirect contact (3 marks)
6 State the earthing systems that use the following as return earth paths
a) PEN conductor (1 mark)
City and Guilds 2391 Sample Paper A
Page 2 of 6
b) cable sheath (1 mark)
c) general mass of earth (1 mark)
7 State the test instruments to be used for the following tests
a) continuity of supplementary bonding in a bathroom (1 mark)
b) external earth fault loop impedance of a TN-C-S system (1 mark)
c) live polarity (1 mark)
8 Give THREE examples of notices/warning labels that should be present in
an electrical installation
(3 marks)
9 State the IP code that applies to the following enclosures
a) accessible horizontal top surfaces (1 mark)
b) internal intermediate barriers (2 marks)
10 The continuity of a lighting circuit c.p.c. is verified using the phase
conductor as part of the test. State the
a) instrument to be used (1 mark)
b) action to be taken regarding the test leads (1 mark)
c) significance of the reading at the furthest point (1 mark)
11 State THREE outcomes of the ring final circuit continuity test. (3 marks)
12 State the test voltage and minimum value of insulation resistance for EACH
of the following
a) 12V fan circuit in a bathroom (1 mark)
b) three-phase commercial installation (1 mark)
c) 800V discharge lighting circuit (1 mark)
13 Give THREE reasons for carrying out a polarity test on an installation, as
required by BS7671 2001
(3 marks)
14 The resistance of an earth electrode is to measured. If a mains supply is
unavailable, state the
a) instrument to be used (1 mark)
b) terms used to describe the TWO other test electrodes. (2 marks)
City and Guilds 2391 Sample Paper A
Page 3 of 6
15 State the maximum disconnection times appropriate to the following
a) a domestic socket outlet circuit (1 mark)
b) site hut lighting on a construction site (1 mark)
c) 110V reduced low-voltage system. (1 mark)
16 State
a) why it may not be possible to obtain a measured value of loop
impedance for a circuit protected by an RCD
(1 mark)
b) how this value may be determined without the use of a special
instrument
(2 marks)
17 A loop impedance test is to be conducted on a radial socket outlet circuit.
State
a) where in the circuit the test should be made (1 mark)
b) TWO conditions that may affect the validity of the measured value as a
comparison to the maximum value
(2 marks)
18 State THREE reasons for the use of a 20mA RCD. (3 marks)
19 In the formula IΔ n = 50/Zs state
a) what is represented by ‘50’ (1 mark)
b) the maximum residual current rating of the RCD required, when the
value of Zs is 500Ω
(2 marks)
20 The PFC at the origin of an installation is to be measured. State the
a) instrument to be used (1 mark)
b) measurement units (1 mark)
c) importance of the breaking capacity of the protective devices at the
origin
(1 mark)
City and Guilds 2391 Sample Paper A
Page 4 of 6
Section B – Answer ALL SIX questions
Questions 21 to 26 all refer to the following scenario and Fig. 1 (attached).
Fig.1 shows the main intake and circuit arrangements for the new electrical installation in a
refurbished dentist’s surgery. The heating, ventilating and air-conditioning unit (HVAC), located
outside the building is supplied using p.c.v./p.c.v./s.w.a. multicore cable. All other circuits are
wired using p.v.c. single-core cables enclosed in concealed p.v.c. conduit and surface trunking
(c.p.c’s are the same size as the phase conductors). The lighting is a mixture of tungsten
filament, fluorescent and PIR-controlled exterior security lights. The installation has been
completed and is ready for inspection and testing.
21 State the
a) type of inspection and test to be completed (1 mark)
b) certificate that will need to be completed (2 marks)
c) signatures that are required on the certificate in b) (3 marks)
d) status of the signatories (2 marks)
e) documents that must accompany the certificate in b) (2 marks)
f) information regarding the incoming supply that should be recorded on
ONE of the documents in e)
(3 marks)
g) person who should keep the original completed documents (2 marks)
22 State
a) the terms used to describe EACH of the following items labelled
i) 1
ii) 2
iii) 3
iv) 4
(4 marks)
b) the earthing system (1 mark)
c) where, on the gas and water supplies, item 2 should be connected (2 marks)
d) the label that should appear at the connection in c) (1 mark)
e) why a type D circuit breaker is used on B9 (3 marks)
f) FOUR relevant items to be considered from the BS7671 2001
installation schedule
(4 marks)
23 List, in the correct sequence, the relevant tests to be carried out on the
installation circuits, indication the instruments to be used for EACH test.
(15 marks)
City and Guilds 2391 Sample Paper A
Page 5 of 6
24 Describe how
a) an insulation resistance test would be carried out on circuit R1 (8 marks)
b) a c.p.c. continuity test would be carried out on circuit Y5 (7 marks)
25 a) The insulation resistance values for circuits R2, B6 and B9 were
3.8MΩ, 4.9Ω and 5.0MΩ respectively. All other circuits were in excess
of 999MΩ. Calculate the approximate value of the overall insulation at
the origin
(7 marks)
b) When the system is energised and before the sequence of live tests is
conducted, it is important to carry out a live polarity test. State
i) the reason for this test
ii) where this test should be conducted
iii) the instrument to be used
iv) why the test will not reveal neutral-earth reversals
(8 marks)
26 The measured values of earth loop impedance for each circuit are as follows:
CIRCUIT 1 2 3 4 5 6 7 8 9 10
MEASURED
VALUES
3.8Ω 2 Ω 2.6 Ω 1.3 Ω 1 Ω 2.5 Ω 2 Ω 1.8 Ω 0.4 Ω 1.2 Ω
a) State the environment and circuit conditions which may have an effect
on these measured values
(4 marks)
b) State how these conditions are compensated for. (1 mark)
c) Show, by calculation, if the measured values are acceptable (5 marks)
d) State a solution for any circuit that fails to comply. (5 marks)
City and Guilds 2391 Sample Paper A
Page 6 of 6
Fig 1

2391 questions sample 5 answers

2011-07-13T02:25:00.001-07:00

Sample questions
1) Indicate three main items for which you would require relevant information about
in order to undertake an initial inspection on a new installation.
Possible Answers
Maximum demand
Earthing system
Diagrams, charts or tables
Nature of supply
2) State relevant documentation that relate to the inspection and test of a system
Name one statutory and two non statutory
Possible Answers
Statutory
Electricity at Work Regulations 1989
Health and Safety at Work act 1974
Non Statutory
IEE Wiring Regulations 17th edition BS7671,
Guidance Note 3,
On Site Guide
Documentation GS38
3) An Electrical Installation Certificate and a Periodic Inspection Report should be
accompanied by two other documents what are they?
Possible Answers
Schedule of inspection
Schedule of test results
4) State three areas of inspection you would check when carrying out a Periodic
Inspection Report
Answers
Priority given to
Safety of person's
livestock
property.
Other possible area's are damage caused through overloading, signs of mechanical
damage, compliance to regulations, damage caused by external influences
Basic and fault protection, isolating devices, conductors, enclosures and mechanical
protection

5).State three human senses used when carrying out a Periodic Inspection Report
Answers
Sight
Smell
Touch
6). List the instruments which provided the measurements 20 Megohms, 8KA and
22mS
Answers
Insulation Resistance Meter
Prospective Short Circuit Current Tester
RCD tester
7) Insulation resistance testing requires different test voltages for certain circuits,
identify what circuits require the following voltages 250v, 500v and 1000v.
Answers
SELV or PELV circuit test at 250 volts and results should be ≥ 0.5 MΩ
Circuits 500v or under test at 500v and results should be ≥ 1 MΩ
Circuits above 500v but below 1000v test at 1000 volts test results should be ≥ 1 MΩ
8) State the first three tests that should be taken during the initial verification of a
new installation.
answers
Continuity of protective conductors and bonding
Continuity of ring circuits
Insulation resistance test
9) The test for continuity of the CPC in a radial circuit with one socket requires a
link and a Milli-ohmmeter state: were link is connected, where the meter is
connected, what the meter reading represents.
Answers
Link connected between Line conductor and CPC at the consumer unit
Meter connected at socket between CPC and Line conductor
R1+R2 value

10) State three different protective conductors that need to be connected to the
main earth terminal
Answers
Circuit Protective Conductor (CPC)
Earthing conductor
Main protective bonding conductor
11) The following results were obtained during the initial test on a healthy ring
circuit
P1 > P2 = 0.8 ohms
N1 > N2 = 0.8 ohms
CPC1 > CPC2 = 0.8 ohms
What readings would you expect after cross connection
Between Line and neutral at each socket?
Between Line and CPC at each socket?
What does the Line and CPC represent? The following results
Answers
0.4 Ohms
0.4 Ohms
R1+R2 for the circuit
12) State the effect on
Conductor resistance when cable length increases
Conductor resistance when CSA increases
Conductor resistance when cable length increases
Answers
Resistance increases
Resistance decreases
Resistance decreases
13) State three precautions to be taken before an insulation resistance test on a
circuit
Answers
No danger to person livestock or property while taking test
Lamps or capacitors are removed from circuit
Voltage sensitive equipment is removed/isolated from circuit
There are no shorts in circuit
All switches are in the closed position

14) An enclosure has been fabricated on site state the minimum IP rating, it is not
affected by liquids
IP4X, IP2X, IPXXB
15) State the protection offered by the following IP ratings IP4X, IPX8, IPXXB
Protection against foreign solid bodies up to 1mm diameter
Protection against total submersion
Protection against finger contact only
16) State three reasons for conducting polarity checks on a circuit
Polarity check on circuit wiring
Polarity check on switch wiring to ensure line conductor switching.
Check on switching in Line conductor
Correct polarity of supply,
Centre contact on Edison lamp live
17) ID earthing system that is connected with overhead cables, a multi core supply
cable with separate earth and neutral, supply in which earth and neutral are
performed in one conductor.
TT
TN-S
TN-C or TN-C-S
18) State three location where additional requirements for an electrical installation
are needed.
Locations which contain bath or shower, caravan site, construction site, agricultural or
horticultural location, swimming pool or any other section in part 7 of BS7671:2008.
Additional requirements are also required in some other locations such as petrol stations
these have other British Standards that apply.
19) From the formula Zs = Ze+(R 1 + R 2 ) x 1.2 x L state what is Ze, R2 and 1.2
1000
Ze, external loop impedance
R2 resistance of the circuit CPC
1.2 is conductor temperature multiplier

20) State three functional test to be carried out on an installation
Switching in Line Conductor
RCD test button
Functional switching
Isolation
21) For carrying out initial verification of the installation. What information or
documentation is required? Where should it be found? What particular uncommon
details should be recorded on this installation? What consideration should be given
to the existing installation from which the new one is fed.?
Charts, diagrams or tables relating to the installation and the results of the general
characteristics.
Should be located in or adjacent to the distribution board
Reference to the electronic door equipment and the PIR which may be sensitive to certain
tests
Maximum demand, earthing systems, overload protection, capacity of consumer unit,
capacity of main protective device, diversity

22) List five areas of inspection that should be undertook before testing
To ensure Safety of person's, livestock and property while testing also
method of fault protection, basic protection, number of circuits, identification of circuits,
methods of isolation, suitability of enclosures, cable selection, fire protection,
23) The electronic door/sensor/motor is wired on its own radial circuit.
List ALL the component parts of the earth fault current loop path associated with
this circuit in the event of a fault to earth
If the maximum value of Earth Loop Impedance for this circuit is 2.4Ω and an earth
fault causes a current of 120A show by calculation if this value will disconnect the
circuit in the required time.

You can then list the path looking at both diagrams
Point of fault
The Circuit Protective Conductor (CPC)
Steel wire armour of the garage supply
Main earthing terminal
Earthing conductor
The metallic return path of the supply cable
The transformer Star point
The transformer winding
Line conductor
Point of fault
We need to use ohms law for the second part, given that the supply is a standard 230 volt
and the current is 120A. Resistance = Volts / Current . 230V / 120A = 1.92 Ω
The maximum allowable is 2.4Ω as we have calculated ours as 1.92 Ω the circuit will
disconnect within the time limitations.
24) The test results shown below were obtained from a ring final circuit continuity
test. State whether the readings for each socket are satisfactory or not satisfactory
giving reasons for those readings deemed to be unsatisfactory. The line, neutral
and the circuit protective conductors have loop test results of 0.5Ω
Socket Line to Neutral Line to CPC
A 0.25 0.26
B NO READING 0.25
C 0.35 0.24
D 0.24 NO READING
E 0.26 0.26
Socket A is ok readings are half of the loop test result of 0.5Ω
Socket B Cross polarity between Line and CP conductor or twisted neutrals not in terminal
Socket C Loose Neutral connection.
Socket D Cross polarity between Line and N conductor or twisted CPC not in terminal
Socket E is ok readings are half of the loop test result of 0.5Ω
25) Describe in detail how you would carry out an insulation resistance test on this
installation.

Inform people or warn that a test is about to take place which may introduce dangerous
voltages and that in the case of a periodic inspection the circuit will be isolated.
Ensure during visual inspection that no damage will occur to People, Livestock or
Property.
Check meters and leads confirm to GS38.
Check meter operation against a known source.
Isolate supply and lockout and place isolation notice on isolator
Confirm isolation using voltage meter.
Remove sensitive equipment from the circuit to be tested, e.g dimmer switches, electronic
devices etc.
Ensure switched are in the on position to ensure all circuits are tested.
The meter to be used is an insulation resistance meter set to 500 volts.
With the main isolator off but all fuses and MCB's switched on, test between the Neutral
and Line conductors at the distribution board
Now connect the line and neutral conductor together and test between them and the
Circuit protective conductor.
26) The test result indicates an overall value of 1.75 MΩ. State with reasons, what
actions if any should be taken.
Because the value is below the 2MΩ limit any circuits tested together must be separated
and re tested to eliminate any latent defects that may exist
27) A loop impedance test on the lighting circuit cannot be carried out because the
6A MCB is tripping under the test voltage, why?
The Earth loop impedance tester uses high current for a short length of time which in
some circumstances can trip low rated MCB out on overload.
28) How can this be overcome?
The value must be calculated by measuring the R1+R2 value and adding this value to the
measured value of Ze
Zs = Ze + (R1+R2)
29) State THREE circumstances that would require a periodic inspection and test to
be carried out on an installation.
Change of use of premises, change of occupation, reason to believe damage has
occurred, loading on installation increased or alterations or additions have occurred to
system, frequency of inspection has based the maximum required time

30) There are various documents that are relevant to the Inspection and Testing of
an installation. State a) one statutory item of documentation b) two non-statutory
items of documentation.
Statutory
Electricity at Work regulations1989,
Non statutory
IEE Wiring regulations BS 7671,
Guidance Note 3
GS38 or The IEE Onsite Guide
31) A Electrical Installation Certificate should be accompanied by signed
documentation regarding thee stages of an installation. Identify
TW0 of these stages
The status of the person signing.
Design, construction or inspection and test ,
Competent person
32) List THREE areas other than wear and tear and ageing that should be
considered when carrying out a periodic inspection and test of an insulation.
Conductor correctly connected and no signs of damage, methods of protection against
basic and fault protection are intact, ID of circuits and isolators no damage by heat
33) BS 7671 gives a list of 18 items to be checked, where relevant, during an initial
inspection. List THREE of these.
Ensure no damage will occur to People, Livestock or Property during visual inspection,
methods of basic and fault protection, correct cable sizing, correct protection against
spread of fire, cable selection correct, routing of cable correct.
34) State the electrical units in which EACH of the following test results would be
expressed.
a) Insulation resistance.
b) loop impedance.
c) Tripping time of an RCD
Megohm (MΩ)
Ohm's (Ω)
Milli-seconds (mS)

35) Identify the type of circuit that would require the following applied voltages
when conducting an insulation resistance test.
a) 250v
b) 500v
c 1000v
a SELV or PELV
b Systems upto and including 500v
c Systems over 500v but under 1000v
36) List the first three tests that should be carried out during periodic inspection
and test of an installation.
Continuity of protective conductors, continuity of bonding conductors, continuity of ring
circuit, insulation resistance
37) Name the protective conductors that connect together the following.
a) An electrically heated towel rail and exposed metal pipework in a bathroom.
b) The earthing terminal of a socket outlet and the main earthing terminal.
c) Mains Gas and Water services to the main earthing terminal.
Supplementary protective bonding conductor
Circuit protective conductor
Main protective bonding conductor
38) State the essential action to be taken before disconnecting a main protective
bonding conductor for test purposes during a periodic inspection and test and
danger that would arise if this action is not taken.
Persons affected should be informed. Supply should be isolated if not fault protection is
compromised which could but people livestock or property in danger. Consideration should
also be taken with regard to potentially dangerous test voltages which may be present
during testing
39) State the
a) Equipment required to conduct a ring final circuit continuity test b) other test that
is automatically completed when the test in a) is carried out c) significance of the
reading obtained between Line conductor and CPC at each socket outlet.
Low ohm meter, polarity checks, Circuit R1+R2 value

40 In the test required to verify the electrical separation of a SELV circuit
a) instrument to be used
b) test voltage to be applied.
Insulation resistance meter,
250v
41) With regards to polarity testing of an installation, state a) the instrument to be
used b) in which conductor all single pole devices should be connected c) to which
part of an Edison screw landholder the neutral conductor should be connected.
Low Ω meter for dead tests and a dedicated test lamps or volt meter both compliant to the
GS38 specification,
Line conductor,
Screw or outer part.

42) The diagram below shows the layout of the electrical installation in a detached
garage. The owners have, for some time been using it for a business venture
repairing lawnmowers, electric and petrol driven. Heating is provided by two 2 kW
convector heaters plugged in when needed. The three Way metal clad consumer
unit houses a double pole main switch and BS 1871 type 2 M.C.B.'s. All surface
wiring is multicore PVC. non-armoured cable clipped direct, and all socket outlets
(these have been raised from their original position to bench level) and lighting
switches are made from moulded plastic.
43) State the a) documentation and information it would be useful to have regarding
this installation b) action to be taken if such documentation is unavailable c)
documentation that will need to be completed for this inspection and test d) test
equipment needed.
Any diagrams charts or tables, Periodic inspection report, schedule of inspections
schedule of test results,
An exploratory investigation would be undertook,

A Low ohm meter, insulation resistance meter, earth loop impedance meter, dedicated test
lamps or voltmeter to GS38 specifications
44 ) State THREE general causes for concern regarding the use of this installation
that would be revealed during a visual inspection.
Briefly explain the reasons for EACH of the concerns listed and for each one
suggest a possible solution.
Lack of RCD protection for use of hand tools, increases shock risk, could rectify by fitting a
30mA RCD.
Mechanical protection on surface mounted cables, again increases risk of shock by
inadequate mechanical protection of a live part, could rectify by installing trunking or
conduit.
Two 2kw heaters if both on equate to 4kw / 240v = 16.6 amps usage, if other appliances
are been used then the ring is close to an overload condition. Install new fixed circuits for
heating.
Mechanical protection for switches and sockets being plastic could be improved. Increases
risk of shock by inadequate mechanical protection of a live part, could rectify by installing
metal clad switches and sockets.
45) Why is it necessary to carry out a ring circuit continuity test in this garage
installation? Describe how the test in a) should be carried out. Indicate the
instrumentation to be used. Which of the test results would be recorded on the test
schedule?
To ensure ring continuity and the existence of no interlinks, loose connections or identify
spurs.
Ensure during visual inspection that no damage will occur to People, Livestock or
Property.
Check meters and leads .
Check meter operation against a known source.
Isolate supply and lockout and place isolation notice on isolator
Confirm isolation using voltage meter that confirms to GS38
Remove the ring circuit ends from the terminals
End to End resistance test are carried out at the ends of each of the ring circuits
Line conductor 1 to Line conductor 2
Neutral conductor 1 to Neutral conductor 2
Circuit Protective conductor 1 to Circuit Protective conductor 2

Line conductor 1 is now connected to Neutral conductor 2
Line conductor 2 is now connected to Neutral conductor 1
Resistance readings are taken at each socket between the Line and Neutral sockets,
these readings should be equal to each other and around half the end to end resistance
figures
The test is repeated using the CPC conductor rather than the Neutral conductor.
Line conductor 1 is now connected to CPC conductor 2
Line conductor 2 is now connected to CPC conductor 1
Resistance readings are taken at each socket between the Line and CPC sockets, these
readings should be equal to each other and around half the end to end resistance figures.
Instrument used was a low ohm meter 4-24v and generating 200mA .
This final test gives us our R1 and R2 values and can be entered in our Schedule of Test
Results and if the results are as required the tick for Ring circuit Ok can be ticked
46) State pre-test precaution before insulation resistance test undertook
insure no danger to persons livestock or property. Isolate supply, insure fuses in place and
switches and are in the on position, remove any lamps, capacitors in circuit. Remove any
sensitive equipment from circuit.
47) Test voltage to be used is 500 volts and minimum expected value would be 1 MΩ for
individual circuits or 2 MΩ for complete circuit
48) Individual circuits give readings of 80M ohm 60M ohm and 30M ohm what is
expected overall resistance. We need to consider that the circuits will be in parallel
with each other when connected to the supply
1 + 1 + 1 = 0.0625 1 = 16M ohm
80 60 30 0.0625
1/80 = 0.0125
1/60 = 0.0166
1/30 = 0.0333
0.0125 + 0.0166 + 0.0333 = 0.0625
1/ 0.625 = 16 which equates to 16 MΩ

49)An inspection is required of a change in builder owner ship. State the
Type of inspection required?
Documentation that will need to be completed?
Periodic inspection report
Periodic inspection report, Schedule of test results, Schedule of inspection.
50) State the three items of technical information that must be recorded on the
Schedule of Test Results, and relate to the incoming supply to the installation.
Type of supply TNC, TT TNC-S
Ze at origin
Prospective Fault Current
51) State with who should the extent and limitations of the inspection and test
should be agreed with?
The person ordering the work.
52) Where should this be recorded?
On the Periodic Inspection Report under the Extent and limitations of the Inspection.
The name of the person ordering the work should be entered in the deceleration section
under the For and behalf of section.

2391 questions sample 5

2011-07-13T02:19:00.001-07:00

Sample questions
1) Indicate three main items for which you would require relevant information about
in order to undertake an initial inspection on a new installation.
2) State relevant documentation that relate to the inspection and test of a system
Name one statutory and two non statutory.
3) An Electrical Installation Certificate and a Periodic Inspection Report should be
accompanied by two other documents what are they?
4) State three areas of inspection you would check when carrying out a periodic
inspection.

5) State three human senses used when carrying out a Periodic Inspection Report
6) List the instruments which provided the measurements 20 Megohms, 8KA and
22mS.
7) Insulation resistance testing requires different test voltages for certain circuits,
identify what circuits require the following voltages 250v, 500v and 1000v.
8) State the first three tests that should be taken during the initial verification of a
new installation.
9) The test for continuity of the CPC in a radial circuit with one socket requires a
link and a Milli-ohmmeter state: were link is connected, where the meter is
connected, what the meter reading represents.

10) State three different protective conductors that need to be connected to the
main earth terminal.
11) The following results were obtained during the initial test on a healthy ring
circuit.
P1 > P2 = 0.8 ohms
N1 > N2 = 0.8 ohms
CPC1 > CPC2 = 0.8 ohms
What readings would you expect after cross connection
Between Line and neutral at each socket?
Between Line and CPC at each socket?
What does the Line and CPC represent? The following results
12) State the effect on, Conductor resistance when cable length increases.
Conductor resistance when CSA increases. Insulation resistance when cable length
increases.
13) State three precautions to be taken before an insulation resistance test on a
circuit.

14) An enclosure has been fabricated on site state the minimum IP rating, it is not
affected by liquids.
15) State the protection offered by the following IP ratings IP4X, IPX8, IPXXB.
16) State three reasons for conducting polarity checks on a circuit.
17) ID earthing system that is connected with overhead cables, a multi core supply
cable with separate earth and neutral, supply in which earth and neutral are
performed in one conductor.
18) State three location were there are additional requirements for an electrical
installation
19) From the formula Zs = Ze+(R 1 + R 2 ) x 1.2 x L state what is Ze, R2 and 1.2
1000

20) State three functional test to be carried out on an installation.
21) Carry out initial verification of the installation.
a. what information/documentation is required
b. were should it be found
c. what particular uncommon details should be recorded on this installation.
d. what consideration should be given to the existing installation from which the new one
is fed.

22) List five areas of inspection that should be undertook before testing
23) The electronic door/sensor/motor is wired on its own radial circuit.
List ALL the component parts of the earth fault current loop path associated with
this circuit in the event of a fault to earth
If the maximum value of Earth Loop Impedance for this circuit is 2.4Ω and an earth
fault causes a current of 120A show by calculation if this value will disconnect the
circuit in the required time.
In questions like this please consider a diagram to help explain to the examiner and
to help you recognise any areas you may have missed.

24) The test results shown below were obtained from a ring final circuit continuity
test. State whether the readings for each socket are satisfactory or not satisfactory
giving reasons for those readings deemed to be unsatisfactory. The line, neutral
and the circuit protective conductors have loop test results of 0.5Ω
Socket Line to Neutral Line to CPC
A 0.25 0.26
B NO READING 0.25
C 0.35 0.24
D 0.24 NO READING
E 0.26 0.26
25) Describe in detail how you would carry out an insulation resistance test on this
installation.
26) The test result indicates an overall value of 1.75 MΩ. State with reasons, what
actions if any should be taken.
27) A loop impedance test on the lighting circuit cannot be carried out because the
6A MCB is tripping under the test voltage, why?
28) How can this be overcome?
29) State THREE circumstances that would require a periodic inspection and test to
be carried out on an installation.

30) There are various documents that are relevant to the Inspection and Testing of
an installation. State a) one statutory item of documentation b) two non-statutory
items of documentation.
31) A Electrical Installation Certificate should be accompanied by signed
documentation regarding thee stages of an installation. Identify
TW0 of these stages
The status of the person signing.
32) List THREE areas other than wear and tear and ageing that should be
considered when carrying out a periodic inspection and test of an insulation.
33) BS 7671 gives a list of 18 items to be checked, where relevant, during an initial
inspection. List THREE of these.
34) State the electrical units in which EACH of the following test results would be
expressed.

35) Identify the type of circuit that would require the following applied voltages
when conducting an insulation resistance test.
a) 250v
b) 500v
c 1000v
36) List the first three tests that should be carried out during periodic inspection
and test of an installation.
37) Name the protective conductors that connect together the following.
a) An electrically heated towel rail and exposed metal pipework in a bathroom.
b) The earthing terminal of a socket outlet and the main earthing terminal.
c) Mains Gas and Water services to the main earthing terminal.
38) State the essential action to be taken before disconnecting a main protective
bonding conductor for test purposes during a periodic inspection and test and
danger that would arise if this action is not taken.
39) State the
a) Equipment required to conduct a ring final circuit continuity test b) other test that
is automatically completed when the test in a) is carried out c) significance of the
reading obtained between Line conductor and CPC at each socket outlet.

40 In the test required to verify the electrical separation of a SELV circuit
a) instrument to be used
b) test voltage to be applied.
41) With regards to polarity testing of an installation, state a) the instrument to be
used b) in which conductor all single pole devices should be connected c) to which
part of an Edison screw landholder the neutral conductor should be connected.

42) The diagram below shows the layout of the electrical installation in a detached
garage. The owners have, for some time been using it for a business venture
repairing lawnmowers, electric and petrol driven. Heating is provided by two 2 kW
convector heaters plugged in when needed. The three Way metal clad consumer
unit houses a double pole main switch and BS 1871 type 2 M.C.B.'s. All surface
wiring is multicore PVC. non-armoured cable clipped direct, and all socket outlets
(these have been raised from their original position to bench level) and lighting
switches are made from moulded plastic.
43) State the a) documentation and information it would be useful to have regarding
this installation b) action to be taken if such documentation is unavailable c)
documentation that will need to be completed for this inspection and test d) test
equipment needed.

44 ) State THREE general causes for concern regarding the use of this installation
that would be revealed during a visual inspection.
Briefly explain the reasons for EACH of the concerns listed and for each one
suggest a possible solution.
45) Why is it necessary to carry out a ring circuit continuity test in this garage
installation? Describe how the test in a) should be carried out. Indicate the
instrumentation to be used. Which of the test results would be recorded on the test
schedule?

46) State pre-test precaution before insulation resistance test undertook
47) Test voltage to be used
48) Individual circuits give readings of 80M ohm 60M ohm and 30M ohm what is
expected overall resistance. We need to consider that the circuits will be in parallel
with each other when connected to the supply.

49)An inspection is required of a change in builder owner ship. State the
Type of inspection required?
Documentation that will need to be completed?
50) State the three items of technical information that must be recorded on the
Schedule of Test Results, and relate to the incoming supply to the installation.
51) State with who should the extent and limitations of the inspection and test
should be agreed with?
52) Where should this be recorded?

2391 questions sample 4

2011-07-13T02:15:00.001-07:00

City and Guilds 2391 Sample Paper D
Page 1 of 5
This examination consists of two sections.
Section A - Twenty short answer questions worth three marks each. Candidates must answer ALL TWENTY
questions. It is recommended that candidates allow approximately one hour for this section.
Section B—Six structured questions worth 15 marks each. Candidates must answer ALL SIX questions. It is
recommended that candidates allow approximately 11/2 hours for this section.
Section A - Answer ALL TWENTY questions in this section.
1 An installation has been seriously overloaded and needs investigation.
State the
a) type of inspection and test that would be required (1 mark)
b) certificate that will need to be completed (1 mark)
c) documentation that must accompany the certificate in b) (1 mark)
2 State the
a) statutory document that is relevant to electrical systems (1 mark)
b) non-statutory document that details the use of electrical test
equipment
(1 mark)
c) non-statutory document that sets out the requirements for electrical
installations
(1 mark)
3 State who
a) should decide when the first periodic test on an installation should be
carried out
(1 mark)
b) should decide when further periodic tests on an installation should be
carried out
(1 mark)
c) the extent and limitations of a periodic inspection and test should be
agreed with.
(1 mark)
4 State the form of shock protection offered by the following
a) placing out of reach (1 mark)
b) EEBADS (1 mark)
c) class II equipment (1 mark)
5 State the instruments required for the following tests
a) continuity of ring final circuit conductors (1 mark)
b) insulation resistance (1 mark)
c) live polarity (1 mark)
City and Guilds 2391 Sample Paper D
Page 2 of 5
6 State, apart from loose connections, three circumstances that would result
in an increase in conductor resistance
(3 marks)
7 The c.p.c. continuity of a radial circuit comprising four socket outlets is to
be tested. If the test method uses a temporary link between phase and
earth in the distribution board, state
a) at which points in the circuit the test should be conducted (1 mark)
b) the conductors between which the test should be made (1 mark)
c) the significance of the reading at the farthest point (1 mark)
8 State THREE wiring systems that would not normally require a separate
thermoplastic (p.v.c.) insulated conductor as a CPC
(3 marks)
9 For a ring final circuit, state
a) why the test between P and N is conducted (1 mark)
b) the reason why phase to neutral readings at each socket would
increase towards the mid point of the ring then decrease again
(1 mark)
c) the other test that is automatically conducted (1 mark)
10 For the insulation resistance test on a 230 V installation, state the
a) test voltage to be applied (1 mark)
b) minimum value of resistance acceptable (1 mark)
c) value below which further investigation is required (1 mark)
11 The insulation resistance of 600 V discharge lighting installation is to be
tested, state the
a) test instrument to be used (1 mark)
b) test voltage to be applied (1 mark)
c) minimum value of insulation resistance (1 mark)
12 For an installation in a bathroom, state the
a) type of socket outlet permitted, excluding shaver sockets (1 mark)
b) location of zone 0 (1 mark)
c) rating of an r.c.d. protecting an item of equipment in zone 1 (1 mark)
13 To what IP codes should the following comply?
a) Accessible horizontal top surfaces of enclosures. (1 mark)
b) An intermediate barrier inside an enclosure (2 marks)
City and Guilds 2391 Sample Paper D
Page 3 of 5
14 For the testing of polarity, state why
a) single pole devices should be in the phase conductor only (1 mark)
b) certain modern E14 and E27 lamholders do not require testing (1 mark)
c) a live polarity test is required (1 mark)
15 The total loop impedance of a circuit may be calculated using the following
fomula
1000
( 1+ 2) × ×1.2
Zs = Ze + R R L
a) Ze (1 mark)
b) R2 (1 mark)
c) 1.2 (1 mark)
16 State the
a) important check to be made regarding equipotential bonding carrying
out a loop impedance test on a circuit
(1 mark)
b) action to be taken regarding the earthing conductor prior to
conducting an external loop impedance test
(1 mark)
c) precaution that should be taken before conduction the test in b). (1 mark)
17 A test is to be conducted on a lighting conductor earth electrode. State the
a) instrument to be used (1 mark)
b) other two electrodes used in the test (2 marks)
18 State three circumstances under which an r.c.d. having an operating
current of 30 mA, or less, must be used in an installation
(3 marks)
19 State
a) why a test on an r.c.d. must not be conducted before a loop impedance
test
(1 mark)
b) the reason for a functional test on an r.c.d. (1 mark)
c) the maximum test current that needs to be applied to a 100mA r.c.d. (1 mark)
20 A single-phase T.N.C-S installation has a measured value of external loop
impedance of 0.015 ohms. Show by calculation the expected value of the
prospective fault current.
(3 marks)
City and Guilds 2391 Sample Paper D
Page 4 of 5
Section B Questions 21 to 26 refer to the following scenario. Answer ALL SIX questions. All questions
carry equal marks.
A 15-year-old dry-powder coating factory is situated adjacent to an 11kV/415/240V Regional Electricity
Company substation. The earthing system is T.N-C-S with an external earth fault loop impedance (Ze) of
0.012Ω and a prospective fault current of 20 kA.
The dry-powder coating process involves cleaning metallic components in an acid bath, washing off with water
sprays, drying with hot air blowers, spraying with electrostatically charged powder and finally baking in a
tunnel oven.
The existing installation, which are all radial circuits, is wired with (p.v.c.) conductors in metal conduit and
trunking. Six new lighting circuits supplying high-bay 300W SON luminaires have been installed using a
similar wiring system to the existing installation. The new circuit breakers are fed from a metal clad
distribution board housing BS EN 60898 circuit breakers.
An inspection and test of the whole installation is to be carried out.
21 State
a) the type/s of overall inspection and test required (4 marks)
b) the certification/documentation that needs to be completed by the
inspector
(4 marks)
c) who should receive the originals of these documents (1 mark)
d) who decides when the first periodic test should be conducted on the
new lighting
(1 mark)
e) One statutory and two non-statutory documents relevant to this
inspection and testing process
(3 marks)
f) the status of the inspector (2 marks)
22 State
a) apart from wear, tear and safety, five installation conditions that
would need to be considered during the inspection process
(5 marks)
b) Five items from the BS 7671 schedule of inspections that would need
to be considered
(5 marks)
c) Three human senses that would be used in the inspection process (3 marks)
d) with whom the extent and limitations of an inspection should be
agreed
(2 marks)
23 List
a) the first four relevant tests, in sequence, to be conducted on the new
lighting installation
(7 marks)
b) All relevant test equipment needed for a) (8 marks)
24 a) Describe how an Insulation Resistance test would be carried out on the
new lighting circuits
(5 marks)
b) If an Insulation Resistance test between live conductors and earth on
the whole installation resulted in a test value of 1.6Ω, explain, giving
reasons, any actions to be taken.
(3 marks)
City and Guilds 2391 Sample Paper D
Page 5 of 5
c) Describe how an external loop impedance test should be conducted. (4 marks)
d) Describe how a prospective fault current test should be conducted at
the origin of the installation
(3 marks)
25 The Maximum and measured values of loop impedance for four circuits are
as follows
Max values Measured values
3.43Ω 2.7Ω
2.29Ω 1.7Ω
2.4Ω 1.9Ω
3.75Ω 3.2Ω
a) Explain the reasons for the use of the ‘rule of thumb’ (3 marks)
b) Using the above method, determine if the measured values are
acceptable. (Show all calculations).
(4 marks)
c) For any circuit that fails to comply, indicate two methods of
overcoming the problem.
(6 marks)
26 a) Draw a labeled diagram of the earth fault loop path for any circuit in
the installation.
(8 marks)
b) Explain why it would be appropriate to use BS 3036 fuses in a
distribution board at the origin of this installation
(4 marks)
c) Most standard PSCC testers are designed for single-phase use. How
could an appropriate value of short circuit current between phases be
determined?
(3 marks)

2391 questions sample 3

2011-07-13T02:12:00.001-07:00

City and Guilds 2391 Sample Paper C
Page 1 of 6
This examination consists of two sections.
Section A - Twenty short answer questions worth three marks each. Candidates must answer ALL
TWENTY questions. It is recommended that candidates allow approximately one hour for this
section.
Section B—Six structured questions worth 15 marks each. Candidates must answer ALL SIX
questions. It is recommended that candidates allow approximately 11/2 hours for this section.
Section A - Answer ALL TWENTY questions in this section.
1 State the document that indicates the
a) statutory requirements for electrical systems (1 mark)
b) detailed inspection and testing requirements of BS 7671 (1 mark)
c) selection and use of electricians’ test equipment (1 mark)
2 The owner of a small industrial unit requests an inspection and test for
insurance purposes, Several circuits will be unavailable for testing. State
a) the main document to be completed (1 mark)
b) which part of this document will be of particular importance (1 mark)
c) who should be consulted regarding b) above (1 mark)
3 List the three documents that must be completed after the installation of a
new cooker circuit.
(3 marks)
4 State the three items of technical information that should be recorded on a
minor works certificate, excluding test results.
(3 marks)
5 Identify the form of contact defined by BS 7671 as
a) accidentally touching a live part (1 mark)
b) touching an extraneous conductive part made live due to a fault (1 mark)
c) touching the casing of a class I appliance made live due to a fault (1 mark)
.
6 State the units measured by each of the following instruments
a) low resistance ohmmeter (1 mark)
b) insulation resistance tester (1 mark)
c) RCD tester (1 mark)
City and Guilds 2391 Sample Paper C
Page 2 of 6
7 A new radial socket outlet circuit has been installed. List, in sequence, the
first three instrument tests to be carried out.
(3 marks)
8 State the terms identifying the protective conductor connecting each of the
following
a) TNC-S (PME) supply terminal and the main earthing terminal (MET) (1 mark)
b) MET and the earth terminal of an immersion heater (1 mark)
c) shaver unit and copper pipes in a bathroom (1 mark)
9 State the IP code for an
a) accessible top surface of an enclosure (1 mark)
b) intermediate barrier in a distribution board. (2 marks)
10 A continuity of c.p.c. test (utilising the phase conductor) is to be carried out
on a lighting circuit. State the
a) instrument to be used (1 mark)
b) action to be taken regarding the test leads (1 mark)
c) significance of the reading at the last point. (1 mark)
11 For a standard ring final circuit continuity test, state
a) two reasons for conducting the test (2 marks)
b) the other dead test that is automatically conducted. (1 mark)
12 A twin cable has a phase to neutral insulation resistance value of 100 MΩ
and an individual conductor resistance value of 0.8 Ω. Determine the values, if
the cable
a) was doubled in length (2 marks)
b) length was the same but the conductor cross-sectional area was
halved.
(1 mark)
13 For an insulation resistance test on a SELV circuit, state the
a) instrument to be used (1 mark)
b) test voltage (1 mark)
c) minimum value of insulation resistance (1 mark)
City and Guilds 2391 Sample Paper C
Page 3 of 6
14 An insulation resistance test between P N conductors on three individual
single-phase circuits revealed the following values
0.00 MΩ; 0.08 MΩ; >200 MΩ
What circuit conditions are indicated by these values?
(3 marks)
15 For an earth fault loop impedance test on a new c ircu i t, state
a) why the 3/4 rule is applied (2 marks)
b) if a measured value of 0.7 Ω is acceptable for the circuit maximum of
0.9 Ω.
(1 mark)
16 State
a) the purpose of conducting an earth fault loop impedance test (1 mark)
b) one means of overcoming too high a value of Zs (1 mark)
c) which of the s values measured at socket outlets on a ring final circuit
should be recorded.
(1 mark)
17 State three circumstances that would require the installation of a 30 mA
RCD,
(3 marks)
18 State the three tests to be carried out on a 500 mA RCD. (3 marks)
19 State three methods of determining a value for the prospective fault current
at the origin of an installation.
(3 marks)
20 For a TNC-S system, supplied at 230V, 50 Ha, state
a) why PSCC and PEFC are the same (1 mark)
b) the value of PFC if Ze was 0.01 (1 mark)
c) the approximate value of PFC between phases if the single-phase value
was 10 000A.
(1 mark)
City and Guilds 2391 Sample Paper C
Page 4 of 6
Section B Questions 21 to 26 refer to the following scenario. Answer ALL SIX questions.
All questions carry equal marks.
The inspection and testing of a domestic premises is to be carried out after an existing
consumers’ control unit (c.c.u.), housing BS 3036 fuses, has been replaced and a cooker circuit
added.
The new c.c.u. has a 100A main switch and circuits are now protected by a combination of circuit
breakers and RCBOs. The existing installation is 25 years old and the wiring, together with the
new circuit, comprises flat profile thermoplastic (p.v.c.) cable, clipped direct.
There is an isolator between the supply intake and the c.c.u. A periodic inspection and test was
carried .. out five years previously, where all defects were rectified.
The supply and installation form a TN-S system with measured values of 0.3 Q for Ze, 0.8 kA
for prospective earth fault current (PEFC) and 1.2 kA for prospective short circuit current
(PSCC).
The schedule for the installation is attached (See Fig. 1).
21 a) List all the certification/documentation to be completed by the
inspector.
(4 marks)
b) State who should retain the original copies listed in a). (1 mark)
c) State where a copy of the attached installation schedule should
be kept
(1 mark)
d) State which information regarding shock risk has not been recorded on
the schedule.
(2 marks)
e) State which statutory and non-statutory documents would be relevant
to the inspection and testing process.
(4 marks)
f) State the period of time recommended before the next inspection and
test.
(2 marks)
g) Give one reason why an inspection and test may be required before the
next due date.
(1 mark)
22 a) State why the existing installation will need an inspection and test.
(5 marks)
b) List five items from the BS 7671 schedule of inspections relevant to the
new cooker circuit.
(5 marks)
c) Identify a practical electrical problem commonly encountered when
replacing the c.c.u.
(2 marks)
d) Explain how the installer could have overcome the problem in c). (3 marks)
23 a) i) List, in sequence, the tests required on the cooker circuit (4 marks)
ii) State the test instruments used and the measured units. (6 marks)
b) State the details that should be recorded on a schedule of test results
regarding
i) the test instruments (2 marks)
ii) details of the supply (3 marks)
City and Guilds 2391 Sample Paper C
Page 5 of 6
24 a) Describe how an insulation resistance test would be conducted on the
whole installation.
(8 marks)
b) Individual circuit test values are tabulated as shown below.
Circuit 1 2 3 4 5 6 7 8
MΩ 100 4 10 3 5 100 5 100
What would be the approximate overall value?
(4 marks)
c) State if the value in b) is acceptable, giving reasons/comments (show
all calculations).
(3 marks)
25 a) Explain the particular importance of the earth fault loop impedance
test on circuits of the existing installation now that the c.c.u. has been
changed.
(3 marks)
b) State
i) the conditions that need to be taken into account when comparing
measured and maximum values of Zs
(2 marks)
ii) how this comparison is simply achieved. (1 mark)
c) Refer to the measured values, tabulated below.
Circuit 1 2 3 4 5 6 7 8
Measured
Zs
0.8 1.1 1.3 6.2 5.1 2 0.6 1.3
Calculate these values are acceptable.
(3 marks)
d) Should any Zs value given in c) not comply with BS 7671, state how
this situation may be overcome.
(2 marks)
e) State
i) why it may not be possible to conduct an earth fault loop
impedance test on the lighting circuits
(2 marks)
ii) how this problem may be resolved. (2 marks)
26 State
a) i) the reasons why circuits 2, 3 and 8 are protected by 30 mA
RCBOs, and the others are not
(5 marks)
ii) the test currents to be applied and the maximum operating times
for these RCBOs
(3 marks)
b) i) why there is a difference between the PEFC and PSCC
(5 marks)
ii) which of these two values should be recorded on a schedule of
test results.
(2 marks)
City and Guilds 2391 Sample Paper C
Page 6 of 6
T-NS 100A Main Switch
Circuit Description Points Cable
mm2
Cpc
mm2
Type Protection Rating Maz
Zs
Ω
1 Cooker 1 6.0 4 pvc cb BS EN 60898-B 40A 1.2
2 S/O’s Up 10 2.5 1.5 pvc RCBO BS EN
61009
32A/30mA 1.5
3 S/O’s Down 16 2.5 1.5 pvc RCBO BS EN
61009
32A/30mA 1.5
4 Lights Up 6 1.0 1 pvc cb BS EN 60898-B 6A 8
5 Lights Down 8 1.0 1 pvc cb BS EN 60898-B 6A 8
6 Imm. Htr 1 1.5 1 pvc cb BS EN 60898-B 16A 3
7 Shower 1 10.0 4 pvc cb BS EN 60898-B 50A 0.96
8 Garage 1 4.0 2.5 SWA RCBO BS EN
61009
32A/30mA 1.5
FIG 1

Guidance Note 3: Inspection & Testing

2391 questions sample 2

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2391 questions sample1

2011-07-13T02:07:00.000-07:00

Section - Answer all twenty questions.
1. Three single socket outlets have been added to a ring final circuit.
State the:
a. inspection and test certificate that will need to be completed
b. title in law given to the inspector
c. legal status of the inspector
2. State the: a. statutory document that is relevant to Inspection and Testing b. non-statutory document that is relevant to electrical test equipment c. non-statutory document that is relevant to The Requirements for Electrical Installations
3. Give one example of the circumstances that would require the issue of each of
the following
a. electrical installation certificate.
b. periodic test report.
c. minor works certificate.
4. State:
a. the meaning of indirect contact b. two methods of protecting against indirect contact
5. State the form of protection that is offered by each of the following:
a. placing out of reach
b. SELV
6. Give one example of each of the following
a. an exposed conductive part b. an extraneous conductive part c. direct contact.
7. State the earthing systems that use the following as earth return paths
a. PEN conductor b. cable sheath c. general mass of earth
8. State the measuring instruments that indicate each of the following units
a. MΩ
b. kA
c. ms.
9. From the BS 7671 2001 schedule of Inspections, state three checks to be made on conductors / cables
10. The initial values recorded between the ends of individual P and N loops during
a ring final circuit test were both 0.6ohms. If the cable is flat twin with c.p.c.,
state the;
a. approximate resistance value of the c.p.c. loop
b. approximate values that would be obtained between P and N at each socket after cross-connections bad been made c. reason why P to c.p.c. readings will increase slightly to the mid-point of the ring and then decrease again.
11. The continuity of a lighting circuit protective conductor is to be tested. If the test method uses a temporary link between phase and earth in the distribution board, state
a. at which points in the circuit the test should be conducted
b. the conductors between which the test should be made
c .the significance of the reading at the end of the circuit
12. The insulation resistance of a 12V PELV installation is to be tested. State
a. the instrument that should be used
b. minimum acceptable value of insulation resistance
c. test voltage to be applied.
13. Give three reasons for carrying out a polarity test on an
Installation as required by BS7671 2001.
14. With regards to BS 7671 identify
a. two special locations that require reduced disconnection times for
protective devices
b. one special location that prohibits the use of socket outlets other than
SELV socket outlets.
15. State the
a. important check to be made regarding equipotential bonding before
carrying out a loop impedance test on a circuit
b. action to be taken regarding the earthing conductor prior to conducting
an external loop impedance test
c. precaution that should be taken before conducting the test in b.
16. State the maximum disconnection times appropriate to the following
a domestic socket outlet circuit
b. site hut lighting on a construction site
c. 110v reduced low voltage system.
17. An earth electrode resistance test is to be performed using an earth electrode resistance tester. Name the three electrodes involved in the test.
18. For a TNC-S system, state three parts of the earth fault loop path external to the installation.
19. State three reasons for the use of a 5OOmA r.c.d. in an installation
20. State three methods of ascertaining the value of prospective short circuit current at the origin of a TNC-S system.
Section B Questions 21 to 26 all refer to the following scenario.
A small, 10 year-old, commercial/office premises at 27 Old Street, Littleton, has been sold and the new owner/occupier, Mr. A.N. Other, has requested an electrical inspection and test for insurance purposes. The installation has remained unaltered since new but the original certificates/documents have been mislaid
The supply system is single phase, 2-wire, 230V 50Hz, TN-C-S with measured values for PFC and Ze of 3000A and 0.08Ω respectively.
The suppliers’ protective device is a 100A BS 1361 fuse and the copper, earthing and main equipotential bonding conductors (16mm2) and 10mm2) respectively, have been correctly connected. The other services to the premises are Gas and Water.
The main 230V/100A 2-pole switch is incorporated in a six-way split load distribution board incorporating & 63A/3OmA RCD. This unit is fully accessible and located in the entrance lobby.
The installation comprises 3 No. 32A 4.Omm2 radial socket outlet circuits ( 1 and 2 are RCD protected), a 16A 2.5mm2 radial water heater circuit and 2 - 6A 1.0mm2 lighting circuits (circuit5 supplies an exterior PIR controlled luminaire). All are wired in thermoplastic (pvc) single conductors enclosed in pvc conduit (cpc’s same size as lives) All protective devices are Type ‘2’ BS3871 (M6) miniature circuit breakers.
The client requests that radial S/0 circuit 3 should not be isolated for testing, as it feeds important IT equipment.
The only installation fault revealed during an inspection process was the omission of red sleeving on lighting switch conductors and two-way lighting strappers.
Polarity has been proven to be correct for all circuits, and all functional tests were satisfactory
The test instrument used was a 4in 1 multi. Function tester serial No. A8B489.
The following table indicates the test results obtained
Circuit R1+R2 Max. Zs Test Zs L/L Ins. Res. L/E RCD IΔn RCD 5xIΔn
Ω Ω Ω MΩ MΩ Ms. Ms.
1.Sockets 0.33 1.07 0.42 200 200 260 80
2.Sockets 0.25 1.07 0.35 200 200
3.Sockets ? 1.07 0.7 ? ?
4. Lighting 1.1 5.71 1.2 200 50
5. Lighting 1.3 5.71 3.7 200 50
6. Water H 0.35 3.75 0.46 200 50

21. Complete the attached Schedule of Inspection (Form 3), indicating only those items that are relevant to this installation.
22. State:
a. if the measured values of Zs are acceptable (show all calculations)
b. any value of Zs that maybe suspect, indicating why and giving a possible
reason.
c. why it may not have been possible to obtain values for Zs for circuits 1 and 2
d. how the situation in c) may be overcome.
23. If an Insulation Resistance test on the whole installation had been possible, and the overall value between live conductors was greater than 200MΩ, and that between live conductors and earth was 9MΩ, calculate the theoretical values for circuit 3 (show all calculations).
24. Explain why
a) a 3OmARCD has been used on circuits 1 and 2 rather than one of a higher IΔn value
b) the installed RCD is unsuitable.
25 Complete the attached Schedule of Inspections (Form 4), making appropriate comments in the remarks column.
26 Complete the attached Periodic Inspection Report (Form 6).

2391 introduction

2011-07-13T01:48:00.000-07:00

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Introduction
The notes for this course have been drawn up to aid electricians in their understanding of
the requirements for testing as detailed in Part 6 of IEE Wiring Regulations, 17th Edition
(BS7671 : 2008).
References for the tests described have been taken from Guidance Notes No 3 entitled
'Inspection and Testing' published by the Institute of Electrical engineers.
Whilst every effort has been made to ensure that the information given in these notes is
correct and complete all parties making use of these notes should rely on their own skill
and judgment when using them.
These notes are not intended to replace the need for the 17th edition of the IEE Wiring
Regulations which should be referred to as the definitive source for questions arising in
relation to electrical installations.

Index
Chapter 1 Standards & Regulations
1.1 Standards page 4
1.2 Plan of the IEE Wiring Regulations page 5
1.3 Safety page 6
1.4 Competent Persons page 7
Chapter 2 Earthing Systems
2.1 Reasons for Earthing
2.2 Earth Fault Path
2.3 Earthing Arrangements
Chapter 3 Inspection
3.1 General Requirements
3.2 Initial Inspection
3.3 Periodic Inspection
3.4 Frequency of Inspection & testing
Chapter 4 Testing
4.1 Sequence for Testing
4.2 Continuity of Protective Conductors
4.3 Continuity of Ring Final Circuit Conductors
4.4 Insulation Resistance
4.5 Site Applied Insulation
Protection by Separation of Circuits
Protection by Barriers or Enclosures
Insulation of Non-conducting Locations
4.6 Polarity
4.7 Earth Electrode Resistance
4.8 Earth Fault Loop Impedance
External Earth Fault Loop Impedance
Prospective Short Circuit Current
4.9 Residual Current Devices
4.10 Functional Tests
4.11 Periodic Tests

Chapter 5 Documentation
5.1 Electrical Installation Certificate
5.2 Alterations and Additions
5.3 Periodic Inspection Report
5.4 Minor Works
Chapter 6 Instrumentation requirements

1.1– Standards
It is necessary to understand the reasons for producing regulations which specify
standardized methods associated with the installation, inspection and testing of electrical
installations.
The Electricity Supply Regulations, 1988 and Electricity at Work Regulations, 1989, are
statutory regulations which have to be complied with in terms of safety and workmanship.
An electrical installation which complies with the 17 th Edition of the IEE Wiring
Regulations is viewed by the HSE as likely to achieve conformity with the relevant parts of
the Electricity at Work Regulations, 1989.
Certain types of premises, such as petrol stations, cinemas, night clubs etc.,are subject to
licensing. With this type of premises, statutory regulations which may add to, or differ from
the requirements of the IEE Wiring Regulations, apply. In this case the licensing
requirements would take precedence over the IEE Wiring Regulations.
ln certain areas of electrical work, where the requirements of the IEE Wiring Regulations
are not specific enough, reference will need to be made to the relevant British Standard
covering that subject.
ln addition to the above, due to the UK's membership of the EEC, it is seen as essential
that electrical installation practice be standardized throughout the Community.
CENELEC, the specifying and standards authority for all electrical technical matters for
Europe, have produced Harmonization Documents. In the preface to the IEE Wiring
Regulations these documents and their direct comparison with the relevant parts of the IEE
Wiring Regulations are listed.
Whilst differences of opinion do exist between the IEE Wiring Regulations Committee and
CENELEC on certain subjects, in theory a knowledge of the IEE Wiring Regulations will
enable an electrician to work in any Country within the EEC and to produce work which is
acceptable to the inspection authorities within that county.
By the acceptance of the IEE Wiring Regulations as a British Standard in October of 1992,
the regulations took on the required international standing. This now means that
electricians from other parts of the EEC wishing to carry out electrical work within the UK
are also bound by the IEE Wiring Regulations.

1.2 Plan of the IEE Wiring regulations
Whilst standardization is desirable, it does pose problems. The 17th Edition of the IEE
Wiring Regulations have been laid out according to the pattern agreed for CENELEC
documents which does not always make it easy for one to locate all the regulations
pertaining to a specific topic as these may not be located within the same section.
The major advantage of the current edition of the IEE Wiring Regulations over previous
versions is that it does contain a much improved index.
The Regulation numbers are set out in the arrangement as defined by the internationally
agreed standard for electrical installations, for example.
413.03.03
4 th part (Protection for safety)
Chapter 1 (Protection against electric shock)
Section 3 of chapter (Protective measure: Electrical separation)
Regulation 3 (Requirements for fault protection)
Finally part 3 of the regulation. (Live parts of a separated circuit shall not be connected to
any other circuit or to Earth or to a protective conductor)
The 17th Edition I.E.E. Wiring Regulations or BS7671 can be divided into 7 different
sections.
Part 1 Scope,object & fundamental Requirements for Safety
Part 2 Definitions
Part 3 Assessment of General Characteristics
Part 4 Protection for Safety
Part 5 Selection & Erection Of Equipment
Part 6 Inspection &Testing (Part 7 in the 16th edition)
Part 7 Special Installations or Locations (Part 6 in the 16th edition)
Appendices tables and information required to design a system
Part 1. Scope,Object & Fundamental Requirements For Safety
Chapter 11 - Scope.
Chapter 12 - Objects & Effects.
Chapter 13- Fundamental Principles.

Part 2
Definitions
Part 3. Assessment of General Characteristics
Chapter 31 - Purpose, supplies & Structure
Chapter 32 - Classification of External Influences
Chapter 33 - Compatibility
Chapter 34 - Maintainability
Chapter 35 - Safety Services
Chapter 36 - Continuity of service.
Part 4. Protection For Safety
Chapter 41 - Protection Against Electric Shock
Chapter 42 - Protection Against Thermal Effects
Chapter 43 - Protection Against Over current
Chapter 44 - Protection Against Voltage disturbances and electromagnetic disturbances.
Part 5. Selection & Erection of Equipment
Chapter 51 - Common Rules
Chapter 52 - Selection & Erection of Wiring Systems
Chapter 53 - Protection, isolation, switching, control and monitoring.
Chapter 54 - Earthing Arrangements & Protective Conductors
Chapter 55 - Other Equipment
Chapter 56 - Supplies for Safety Services
Part 6. Inspection & Testing (was part 7 in 16th edition)
Chapter 61 - Initial Verification
Chapter 62 - Periodic Inspection & Testing
Chapter 63 - Certification & Reporting
Part 7. Special Installations Or Locations (was part 6 in 16th edition)
Section 700 - General
Section 701 - Locations Containing a Bath or a Shower
Section 702 - Swimming Pools and other basins
Section 703 - Rooms and cabins containing Sauna heaters
Section 704 - Construction and demolition Site Installations
Section 705 - Agricultural & Horticultural Premises
Section 706 - Conductive locations with Restrictive movements
Section 708 -Electrical Installations in Caravan, camping parks and similar locations.

Part 7. Special Installations Or Locations(cont)
Section 709 - Marinas and similar locations
Section 710 – Medical locations Reserved for Future Use
Section 711 - Exhibition installation's, shows, stands, displays.
Section 712 - Solar Photovoltaic (PV) power supply systems (solar power)
Section 717 - Mobile or transportable unit.
Section 721 - Electrical installations in Caravans and Motor Caravans.
Section 740 - Temporary Installation's for structures, amusements and devices used at
fairgrounds, amusements and circuses
Section 753 - Floor and Ceiling heating systems
Appendices
1 British Standards to which reference is made in the Regulations.
2 Statutory Regulations & associated memorandums.
3 Time/current characteristics of overcurrent protective devices & RCDs
4 Current carrying capacity and volt drop for cables & flexible cords.
5 Classification of external influences.
6 Model forms for certification and reporting.
7. Harmonized cable colours
8 Current carrying capacity and volt drop for busbar trunking and powertrack systems.
9 Definitions multiple source, DC and other systems.
10 Protection of conductors in parallel against overcurrent.
11 Effect of harmonic currents on balances in 3 phase systems
12 Voltage drop in customers installations
13 Methods of measuring the installation resistance or impedance of floors and walls to
earth or to the protective conductor system.
14 Measurement of fault loop impedance with consideration on the increase in resistance
to the conductors with the increase in temperature.
15 Ring and radial final circuit arrangements, Regulation 433.1
The IEE also publish a set of and guidance notes to be used in conjunction with the
regulations.
1 Selection and erection of equipment
2 Isolation and switching
3 Inspection and Testing
4 Protection against fire
5 Protection against electric shock
6 Protection against overcurrent
7 Special locations
The On Site guide published by the IEE provides a short form guide for installations up to
100 amps per phase. It also includes many useful tables and checklists.

1.3 Safety
Electrical testing involves some degree of hazard both to oneself and to other people. As
the regulations primary concern is with the safety of persons, livestock and property, safe
working practices are a must. Safety procedures as detailed in the HSE Guidance Note
GS38 Electrical test equipment for use by electricians' should be observed at all times.
As regards fundamental safety, special note should be taken of Chapter 13 of the IEE
Wiring Regulations BS7671 (page 14) and this should then be compared with the
requirements of the EAWR,1989. It will be seen that these two documents exist in total
harmony as to their aims in regard to the safe use of electricity.
1.4 Competent, Person's Responsible for Inspection and Testing
As we progress through the course it will be appreciated that the person carrying out the
inspection and test of the installation will be responsible for deciding whether or not an
installation complies with the regulations in their entirety.
These course notes will be concentrating on Part 6 of the Regulations. These notes can
not be viewed as a replacement for the Regulations nor can they replace the need for a
sound working knowledge of the Regulations. It will seen that reference must be made to
the other Parts and Appendices within the Regulations other than Part 6.
Therefore the person carrying out the installation (IEE reg 134.1.1 page 19) and the
inspection and testing of any electrical installation work must competent (IEE reg 610.5
page 156). Competency encompasses skills, experience and technical knowledge. The
inspector needs to have experience and knowledge of the type of installation he will be
working on so as to ensure that danger to persons, livestock or property does not occur.

2.1 Reason for Earthing?
The ground under our feet, in fact the whole world can be considered as a conductor which
is at zero potential.
A shock hazard occurs when a person makes contact with two points which are at different
potentials. As people are in contact with the ground which is at zero potential there is a
danger that touching any other surface that may be at a different potential to this will result
in a shock being encountered.
By connecting all those parts, which may become charged to a different potential, to the
general mass of earth, we will do away with the possibilities of shock hazard. By the use of
earthing we also aim to provide a low resistance path for fault currents to flow through,
enabling a high current to flow and the protective device to open.
Electricity always takes the easiest path whether it is through the human body or through
the intended earth conductor. From this we can see the importance of keeping the
impedance of earth paths as low as possible.
The standard method of tying the electrical supply system to earth is by making a direct
connection between the two. This usually entails connecting the neutral or start point of the
three phage supply transformer to earth.
From this we can be fairly certain that the neutral of the system is at, or near zero volts and
that the line conductor will differ from this by 230 volts. We can also see that neutral and
earth will be at the same potential.
By connecting all metal work not intended to carry current to earth by means of protective
conductor, a path is provided for fault currents to flow. This is illustrated and discussed in
the next section.

2.2 Earth loop path
The earth fault loop of a circuit (Zs) includes the following,
Starting from the fault point:
The fault point
The circuit protective conductor
The main earthing terminal
The main earthing conductor
The earth return path
The path through the earth and neutral point of the transformer
The transformer winding
The line conductor from the transformer to the point of fault.
See diagram on page 11

Of what use to us is the measuring of the earth fault loop or Zs of a circuit?

If we know the value of it we can use Ohms Law to calculate the fault current that will flow
if a fault occurs.
The formula we can apply is: voltage = current
resistance
From this we can see that Fault Current and Earth Fault Loop Impedance are directly
linked, the lower the earth fault loop the higher the fault current and vice versa.
Therefore, the lower the earth fault loop, the higher the fault current, the quicker the
protective device will operate to cut off the current. If we limit the maximum value of the
earth fault loop we can be confident that the fault current will be of a higher magnitude to
operate the protective device before dangerous shock can occur.(IEE reg 411.3.2 page 46)
The values of Earth loop impedance are compared to tables in the regulations to determine
the required disconnection times are achieved. (IEE reg Table 41.2 page 48)
For example if a BS 1361 fuse is to be used as our protective device, for a disconnection
time of less than 0.4 seconds in a circuit with a Uo of 230 volts and rated at 20 amps the
maximum Zs value is 1.70 Ω.
More values for disconnection times can be found in Appendix 3 which have graphs and
tables for most of the common types of protective devices.
Using a BS 1361, 20 amp fuse, for a disconnection time of 0.1 sec what current would be
required to flow in order to satisfy the 0.1 second disconnection time?
IEE reg fig 3.1 (page 244) shows a graph and a table. The graph plot start at 0.1 sec and
for a 20 amp fuse it intersects the current lines at just under the 200 amp mark.
This can be confirmed by examining the table in the far right hand corner which confirms
that a current of 180 amps must flow to enable the fuse to disconnect within 0.1 seconds.

2.3 Earthing Arrangements
Electrical systems are classified according to their earthing arrangements. The following
letter designations are used:
The first letter indicates the Supply earthing arrangements.
T One or more points of the supply are directly connected to earth
I supply system not earthed, or one point earthed through a fault
limiting impedance. (Not used in this Country)
The second letter indicates the Installation earthing arrangements
T exposed conductive parts connected directly to earth
N exposed conductive parts connected directly to the earthed point of
the source of the electrical supply.
The third letter indicates the Earthed Supply Conductor arrangement
S separate neutral and protective conductors
C neutral and protective conductors combined in a single conductor.
The types of system detailed in the Wiring Regulations are: IEE part 2 definitions (page
32)
TN-S TN-C-S TN-C TT IT

TN-S System
With this system the neutral and CPC are separate throughout the system. This type of
system applies to underground cables where the metal sheath of the supply cable is
connected to the consumers earth terminal and therefore provides a continuous earth path
back to the star point of the supply transformer.
TT Systems
With this system the Supply Company do not provide an earth terminal. The supply is
usually via overhead lines. The consumer has to provide an electrode to connect the
protective conductors of the installation to earth. Effective earth connection is sometimes
difficult to obtain so therefore a residual current device will need to be installed.

TN-C-S Systems
With this system the Supply Company uses a combined protective and neutral (PEN)
conductor, at this stage the supply is a TN-C system. The consumer installation will consist
of separate neutral and protective conductors (TN-S). This combination is known as TN-CS.
The majority of new installations are of this type and are referred to as a PME supply.
TN-C
With this system the neutral and protective conductors are combined in a single conductor
throughout the installation. This type of arrangement can only be used with permission
from the appropriate authority.
IT Systems
This type of system has either no earth connection or is connected via a high impedance.
This type of system is not allowable in the UK but is included in the Regulations for
European harmonization.

3.1- General Requirement
IEE reg 610.1 (page 156) Every installation shall, during erection and/or on completion
before being put into service be inspected and tested to verify, so far as reasonably
practicable, that the requirements of the Regulations have been met.
The reasons for an inspection and test of an electrical installation is to verify that the
installation complies with the Regulations with regard to its Design and Construction. To
help the person carrying out the inspection to for fill these requirements the Regulations
call for the following Information to be made available:
The results of the assessment of general characteristics required by sections 311,312 and
313.
This would include:
1.The Maximum demand for the installation
2.The Number and type of live conductors ie, single phase two wire ac. Three phase four
wire ac.
3.Type of earthing arrangement ice. TN-C-S TN-S TN-S (See Chapter 2.3)
4.Nominal Voltage
5.Nature of current and frequency
6. Prospective Short Circuit Current at the origin of the installation
7. External Earth Fault Loop impedance Ze (see Chapter 4.8)
8. Type and rating of overcurrent device at the origin of the installation.
The Regulations also call for the information to a be made available as (IEE reg 514.9
page 93).This may be in the form of a chart. This would provide all the necessary
information as to circuit type, number of points and their positions, cable sizes, protective
device types and their ratings etc.
Without the above information the person responsible for the inspection will not be able to
carry out his job.

3.2 Initial Inspection
IEE reg 611.1 (page 156) Inspection shall precede testing and shall normally be done with
that part of the installation disconnected from the supply.
Guidance Note 3 suggests some 180 items to which special attention should be paid
during the Inspection process. From this it can be seen that a complete and concise list is
impossible to compile.
In the majority of cases deviations from the Regulations which one will come across while
carrying out the inspection will be down to the experience of the inspector rather than the
ticking of a checklist. From our discussions so far you will see that experience as well as a
sound working knowledge of the Regulations is a must.
It should always be in mind that the Regulations state (IEE reg 134.1.1 page 19)
Good workmanship by a competent person or persons under their supervision and proper
materials shall be used.
(IEE reg 612.2 page 156) calls for the inspector to confirm that equipment has been
selected in accordance with section 511 of the Wiring Regulations, and the equipment's
compliance with the relevant British or equivalent Standard.
It also calls for confirmation that, this equipment has been correctly selected and installed,
is suitable for the environment, and has no visible damage that may impair safety.
It can be seen from this that the Inspector has immense responsibility placed upon him as
to the safety of the installation.
Visual Inspection is essential to assess the safety of an installation before testing takes
place.

(IEE reg 611.3 page 156) The inspection shall include at least the checking of the following
items, where relevant to the installation and, where necessary, during erection.
It should be noted from the above that the inspection of some of the items can only be
carried out during installation as they will be hidden from view upon completion.
The minimum inspection should include where relevant the following items:
1) Connection of conductors
2) Identification of conductors
3) Routing of cables in safe zones or protection against mechanical damage
4) Selection of conductors for current-carrying capacity and voltage drop, in accordance
with the design
5) Connection of single-pole devices for protection or switching in line conductors only
6) Correct connection of accessories and equipment
7) Presence of fire barriers and protection against thermal ejects
8) Methods of protection against electric shock
9) Prevention of mutual detrimental influences
10) Presence of appropriate devices for isolation and switching correctly located.
11) Presence of undervoltage protective devices.
12) Labelling of protective devices switches and terminals.
13) Selection of equipment and protective measures appropriate to external influences.
14) Adequacy of access to switchgear and equipment.
15) Presence of danger notices and other warning signs.
16) Presence of diagrams, instructions and similar information.
17) Erection methods.
(a) Method for Basic and Fault protection, i.e
SELV
Limitation of discharge energy
(b) Method for Basic protection (including measurement of distances where
appropriate), i.e:
Protection by insulation of live parts
Protection by a barrier or an enclosures
Protection by obstruction
Protection by placing our of reach
Protection by PELV

c) Method for Fault protection.
Earthed equipotential bonding and automatic disconnection of supply Presence of earthing
conductors
Presence of protective conductors
Presence of main equipotential bonding conductors
Presence of supplementary equipotential bonding conductors
Presence of earthing arrangements for combined protective and functional purposes
Use of class 2 equipment or equivalent insulation
Non-conducting location (including measurement of distances, where appropriate)
Absence of protective conductors
Earth-free local equipotential bonding
Presence of earth-free equipotential bonding conductors
Electrical separation

3.3- Periodic inspection (IEE chapter 62 page 162)
Periodic inspection is somewhat different to the initial inspection procedure.
The above Regulation refers to 'Careful Scrutiny' backed up by testing.
Visual Inspection is the VITAL initial operation and testing is in support of this Visual
Inspection.
In many cases diagrams and circuit charts will not be available so some exploratory work
will be required. The Visual Inspection shall be concerned with the Verification that the
safety of persons, livestock and property has not or will not be endangered.
A thorough Visual Inspection shall be made of all electrical equipment which is not
concealed. It will include many of the items listed under initial inspection.
It is a requirement of the Regulations that the person ordering the work be informed of the
need for Periodic Inspection and Testing. Installations which are subject to licensing have
mandatory intervals between tests which must be followed. Guidance Note 3 gives
guidance as to recommended intervals.

Table 2.1.5 Recommended initial frequencies of inspection of electrical installations
Type of installation Routine check
sub-clause 2.1.4
Maximum period between
inspections and testing as
necessary
References
(see notes below)
General installations
Domestic
Commercial
Educational establishments
Hospitals
Industrial
Residential accommodation
Offices
Shops
Laboratories
1 year
4 months
1 year
1 year
1 year/ Change of
occupancy
1 year
1 year
1 year
Change of tenancy 10 years
Change of tenancy 5 years
5 years
5 years
5 years
5 years
5 years
5 years
5 years
1,2
1,2
1,2
1
1,2
1,2
1,2
Building open to the public.
Cinemas
Church installations
Leisure complexes
Places of public
entertainment
Restaurants and Hotels
Theatres
Public Houses
Village halls/ Community
Centres
4 months
1 year
4 months
4 months
1 year
4 months
1 year
1 year
1 year
5 year (quinquennially)
1 year
1 year
5 years
1 year
5 years
5 years
2,6,7
2
1,2,6
1,2,6
1,2,6
2,6,7
1,2,6
1,2
External Installations
Agricultural and Horticultural
Caravans
Caravan Parks
Highway power supplies
Marinas
Fish farms
1 year
1 year
6 months
as convenient
4 months
4 months
3 years
3 years
1 year
6 years
1 year
1 year
1,2
1,2,6
1,2
1,2
Special Installations
Emergency Lighting
Fire Alarms
Launderettes
Petrol Filling stations
Construction site installations
Daily/ Monthly
Daily/ weekly/
Monthly
1 year
1 year
3 months
3 years
1 year
1 year
1 year
3 months
2,3,4
2,4,5
1,2,6
1,2,6
1,2
Reference Key
1. Particular attention must be taken to comply with SI 1988 No 1057. The Electricity Supply Regulations 1998 (as amended).
2. SI 1989 No 635. The Electricity at Work Regulations 1989 ( Regulation 4 and Memorandum
3. See BS 5266:Part 1: 1988 Code of Practice for the emergency lighting of premises other than cinemas and certain other specified
premises used for entertainment.
4. Other intervals are recommended for testing operation of batteries and generators
5. See BS5839: Part 1:1988 Code of practice for system design and installation and servicing (Fire detection and alarm systems for
buildings)
6. Local Authority Conditions of Licence
7. SI 19995 No 1129 (Clause 27) The Cinematograph (Safety) regulations.

4,1 - Sequence of Tests
Testing of electrical installations can be divided into two distinct parts:
Tests to be carried out before the supply is connected, or with the supply disconnected.
Within this section the sequence for testing is:
(a) 4.2 Continuity of protective conductors, main and supplementary
bonding
(b) 4.3 Continuity of ring final circuit conductors
(c) 4.4 Insulation resistance
(d) 4.5 Site Applied Insulation
Protection by separation of Circuits
Protection by Barriers or Enclosures Provided During Ere
Insulation of Non-conducting Floors and Walls
(e) polarity
(f) Earth electrode resistance
Once the electrical supply has been connected recheck polarity using a suitable mains
voltmeter then carry out the following tests:
(a) 4.8 Earth fault loop impedance
External Earth Fault Loop Impedance
Prospective Short Circuit Current
(b) 4.9 Residual current operated devices
(c) Functional test of switchgear etc

Isolation
Before continuing with the tests consideration must be taken with the subject of isolation of
the circuit.
When isolating it should be confirmed that after isolation the expected circuits are not live
by the use of a suitable test meter set to the suitable voltage setting.
The isolation method should be locked of by either removal of fuses, which are then
secured. Or the application of a locking device.
A notice should be placed at the isolation point to confirm the circuit is isolated and warning
not to re energize the circuit.
These are important steps in the test procedures, they should be included in any procedure
both in working practice and practical or written examination.
4.2 Continuity of Protective Conductors
(IEE reg 612.2.1 page 158)
The above regulation requires that every protective conductor including bonding
conductors shall be tested to verify that they are electrically sound and correctly
connected,
Note: Guidance Note 3 states that
For cables having conductors of a cross- sectional areas not exceeding 35mm their
inductance can be ignored. Above that figure the inductance becomes significant and an
A/C. Instrument should be used for the measurement.
We are unaware of any Company who at the present time manufactures or sells such an
instrument.
For the purpose of the following tests a continuity tester able to read to a resolution of
0.01ohms is required. The full specification is detailed in the chapter dealing with
Instrumentation Requirements.

Test method 1 - Linking line and CP conductors at the distribution board.
Connect a temporary link between the line and the CPC conductors. Using a low
resistance ohmmeter test between the line and earth terminals at each outlet in the circuit.
The measurement obtained at the furthest point of the circuit should be recorded on the
results schedule. This reading is the value R1+R2.
Points to note
Multi Meter set to the low Ω range
a = Temporary link between line and CPC at the consumer unit.
All fuses should be removed or MCB'S switched off Main switch switched off.
* Ensure Removal of temporary link when testing is complete.

Test Method 2 Long lead Method
Connect one terminal of the ohmmeter to the earth terminal at the distribution board via a
lead long enough to reach the farthest extremity of the circuit under test. The other terminal
is then used to make contact with each outlet on the circuit.
Once the resistance of the test leads is subtracted from the readings the figures can be
recorded.
Points to note
Multi Meter set to the low Ω range
Note All fuses out or MCB'S switched off Main switch turned off

From the foregoing descriptions it can be seen that in the majority of cases Method 1 will
be the preferred method. For the testing of bonding conductors Method 2 is the only
applicable method.
Where the protective conductor has been sized according to the alternative method to
IEE reg 411.3.2 62 page 46 of the Regulations a separate measurement of the protective
conductor is required using Method 2.
lt should be noted that the aforesaid methods of test can only be applied to an 'all insulated'
installation'
Installation's incorporating steel conduit or trucking, m.i.c.c. and swa cables will
introduce parallel earth paths which will effect the test readings.
Precautions will need to be taken to identify and eliminate these effects while testing. It can
be seen from this that this stage of testing may have to take place during the installation
process rather than being left till the end.
Guidance Note 3 contains details of the procedures to be followed when steel conduit, etc.
is relied upon as the protective conductor further test can be summarized as follows:
A standard continuity test as detailed in Tests 1 & 2 above. This should be followed by a
visual inspection along the length of the protective conductor path to identify any obvious
points where problems may arise.
The majority of electricians these days will not choose to use steel conduit, etc as the
protective conductor for a circuit, so the above problems should not arise.

4.3 Continuity of Ring Final Circuit Conductors
(IEE reg 612.2.2 page 158) A test shall be made to verify the continuity of each conductor
including the protective conductor, of every ring dual circuit.
As a rink circuit relies on both sets of three conductors to be connected for the circuit to
meet the design criteria as regards current carry capacity and short circuit protection, and
due to the fact that faults occurring may not be immediately apparent, ie. the circuit will still
function with one 'Live' conductor disconnected, it can be seen that testing is of utmost
importance.
Tests need to be carried out to Confirm that line, neutral as well as CPC form uninterrupted
rings.
Correctly connected ring circuit showing equal current sharing on each leg of the ring.

Possible Dangerous Ring Circuit Faults
Here a brake has occurred in on leg of the ring circuit, this results in the cable on the other
leg of the ring becoming overloaded, especially towards the consumer unit side of the leg,
the load could be 27A .

A bridge in the circuit hides the fact the ring is not complete, this fault would not be picked
up in the test for the continuity of CPC, as tested earlier pages 24 and 25.

Test 1 To Confirm the ring is complete
Each individual leg of the ring needs to be identified. The line conductor of one leg of the
ring is conceded to the neutral conductor of the other at the distribution board. The
resistance is measured between the remaining line and neutral conductors. This test
confirms that both the line and neutral conductors form rings.
Points to note
Multi Meter set to the low Ω range

This above test is repeated using the line conductor and the circuit protective
conductor.
Test 2 to confirm the absence of bridges

lt is possible that Test 1 will indicate that the ring is complete, because of a bridge in the
ring as per page 29. This shortening of the ring could cover up the fact that the ring may be
broken at another point, resulting in an overloading of the cables at that point.
Test 2 confirms that the above situation does not exist.
With the conductors connected as in Test 1, connect the remaining line and neutral
conductor together. The resistance been line and neutral at each outlet is then measured.
This reading will remain substantially the same at each outlet that is incorporated into the
ring provided that no multiple loops exist. This test will also indicate any outlets which may
be connected as a spur to the ring.
The values should be within 0.05 Ω of each other.
Points to note
Multi Meter set to the low Ω range

The above test is repeated using the line conductor and the circuit protective conductor.
The highest reading taken is considered as the measured value of R1+R2.
The values should be within 0.05 Ω of each other.

Results
Where the protective conductor is in the form of a ring, the above two tests will need to be
repeated, substituting the protective conductor for the neutral conductor in each test.
The reading obtained in Test 2 at each outlet between the line conductor and protective
conductor will be equal to the value of R1 + R2 for that circuit and should be recorded. This
result will also be equal to one quarter of the value obtained in Test 1.
When testing between line conductor and protective conductor.
R1+R2 = result of Test 2 = result of test 1
4
While it should be easy to identify each leg where multi core cables are used, this may not
be the case where single core cables are used. An error in identification and connection of
the legs of the ring will be immediately apparent while conducting Test 2.
An error in this respect will show up as progressively increasing readings towards the
midpoint of the ring and then a decrease away from the midpoint. If this encountered then
the error in connection will need to be rectified and both Tests 1 & 2 repeated.

Insulation tests
(IEE reg 612.3 page 158)
These tests are to confirm that the insulation of conductors and equipment is satisfactory
and that short circuits do not exist.
Testing is carried call with an insulations tester that generates the required voltage as
specified in Table 61 of the regulations at a current of 1mA.
In the case of electrical installation up to and including 500V the test voltage required will
also be 500V.
Whereas in the past the Regulations called for various pieces of electrical equipment to be
disconnected from the mains and for lamps etc to be removed this is now recognized as
not always practical.
The Regulations now state that 'where appropriate line and neutral conductors may be
connected together and a test to earth carried out. Simple installations which do not
contain distribution circuits may be tested as a whole rather than as individual circuits.
Although Table 61 calls for an insulation value of not less than 1 megohms for an
installation of up to 500V if the result is below 2 megohms each circuit will need to be
tested separately The-result for individual circuits must exceed 1 megohms.
Example of IEE reg table 61 page 158
Minimum values of insulation resistance and meter test voltage settings
Circuit nominal voltage
(V)
Test voltage D.C
(V)
Minimum insulation
resistance
(MΩ)
SELV and PELV 250 ≥ 0.5
Up to and including 500v
with the exception of the
above systems
500 ≥ 1.0
Above 500v 1000 ≥ 1.0

Insulation test for a complete installation
Points to note
Meter set to a test voltage of 500 volts DC (IEE reg table 61 page 158), for testing a 230
volt circuit
Range set to MΩ
The main switch is isolated
All fuses are in and MCB's switched on.
A temporary link is placed between the line a neutral conductors
All fuses should be left in place or MCB'S switched on Main switch switched off.
• Ensure Removal of temporary link when testing is complete.

•
Three Phase
Testing of three phase circuits involves making a series of tests. The conductors will be
grouped into two groups and an insulation test carried out between the two groups.
Group A Group B
Test 1 Phase 1 Phase 2
Phase 3
Neutral
Test 2 Phase 2 Phase 3 Neutral
Test 3 Phase 3 Neutral
Test 4 Phase 1 Earth
Phase 2
Phase 3
Neutral
Where it is not possible to group conductors as above, they may be tested singularly.

4.5 Other Tests
Guidance Note 3 includes several tests which we do not intend to cover in any great detail
within these course notes. For further details reference should be made to the Guidance
notes.
The relevant tests are as follows:
Site Applied Insulation
This test is only applicable where insulation is applied during installation. It involves the use
of a high voltage tester capable of apply a voltage of 3750 V
Protection be Separation of Circuits
This relates to the testing of SELV and FELV transformers to confirm separation of primary
and secondary parts of the circuit.
Protection by Barriers or Enclosures Provided During Erection
This test does not apply to factory built equipment, but only to those provided on site during
the course of assembly or erection. It is concerned with checking that the enclosure meets
the relevant ip rating.
Protection by a non conducting Location
This deals with insulation of non-conducting floors and walls. It includes details of the
required high voltage testing.

4.6 Polarity Testing
(IEE reg 612.6 page 159) A test of polarity shall be made and it shall be verified that :-
Every fuse and single-pole control and protective device is connected in the line conductor
only,
Center-contact bayonet and Edison screw landholders to BS EN 60238 in circuits having
an earthed neutral conductor have the outer or screwed contacts connected to the neutral
conductor;
Wiring has been correctly connected to socket-outlets and similar accessories.
If a switch or fuse is connected in the Neutral conductor of a circuit rather than in the line
conductor, mains potential voltages will continue to be present throughout the circuit when
the switch is opened or the fuse pulled.
This would give rise to the scenario of a circuit appearing to be 'dead' but in actual fact
posing very real danger.
Use an Ohmmeter or the continuity range of an Insulation and Continuity tester for this
sequence of tests.

Method 1 - Linking the Line and CP conductors at the Distribution Board
The method used here is the same as the test described as method 1 for checking the
continuity of protective inductors. This involves connecting a temporary link between the
line conductor and the protective conductor. And then checking at each outlet, including
switch positions, for a low resistance reading between line and Earth.
Ensure that the circuit is isolated before carrying out this test
Remove the link after the test.

Method 2 - Using a Long Lead
Method 2 involves using a long lead. One end of the long lead is connected to the line
conductor at the distribution board and the other end is connected to one terminal of the
ohmmeters The other lead of the Ohmmeter is then used to check each line connection
throughout the circuit for continuity.
If the tests for ring circuits have been carried out as described, correct connection will
already have been verified and no further testing is required
Ensure that the circuit is isolated before carrying out this test

4.7 Earth Electrode resistance
IEE reg 612.9 page 160 Where protective measures are used which require a knowledge
of the earth electrode resistance, this shall be measured.
Testing to check Compliance with IEE reg: 415.2.2 Page 59
Method 1 Using a Dedicated Earth resistance Tester (Figure 4.7)
The earth electrode under test needs to be disconnected from the earthing system of the
installation. As this electrode is likely to be the primary means of earthing for the
installation, this will necessitate the complete isolation of the installation for safety reasons.
Two temporary earth spikes are driven into the ground for testing purposes. The distance
between these earth spikes is important. If the earth spikes are placed too close together
their resistance areas will overlap and false readings will be obtained.
The first, or 'current' spike is driven into the ground at a distance away, from the electrode
under test , equivalent to 10 times the length of the electrode under test.
ie. for an earth electrode 2 meters long the current spike should be placed 20 meters away
from the electrode under test.
The second, or 'potential' spike, is driven into the ground midway between the electrode
under test and the 'current' spike. The earth electrode resistance tester is connected and a
reading is taken. The 'potential' spike is then moved 10% closer to the earth electrode
under test and another reading taken. The 'potential' spike is then moved 10% closer to the
'current' spike and a final reading taken.
The average of the three readings is taken. If there is a difference greater than 5%
between any of the above three readings and the calculated average, then the test
distance between the earth electrode under test and the 'current' will need to be increased
and the above testing procedure repeated.
Upon Completion, Ensure Bonding is reconnected before switching on the
instillation.
Figure 4.7

Test method 2 Using a Loop Impedance meter
Testing For compliance with IEE reg: 411.4.5 (page 48)
This method is intended as an alternative to method 1 for TT installations where the earth
electrode is used in conjunction with a residual current device to provide fault protection.
As with method 1 the main bonding needs to be disconnected from the equipotential
bonding. This is to eliminate the possibility of erroneous readings due to parallel earth
paths and to ensure that the full test current passes through the earth electrode under test.
A loop impedance tester is connected between the line conductor at the source of the
installation and the earth electrode under test. The impedance reading taken is treated as
the electrode resistance.
Upon Completion, Ensure equipotential Bonding is reconnected before switching
on the installation.

Results
What results should we be looking for?
What we are trying to accomplish with our use of earth electrodes is to make sure that
when a fault occurs the voltage between earthed metalwork and earth will not exceed 50
volts.
Where an RCD with a tripping current of 30mA is used, this means that if we apply Ohms
Law to the problem, we would come up with a theoretical value of 1.666ohms
50 V
0.03 A = 1,666 Ohms
BS 7430 Code of Practice for Earthing suggests that earth electrodes with values
exceeded 220 ohms are prone to be unstable.
Maximum values for earth electrodes will more likely be dictated by other regulations such
as HS(G)41 detailing petrol station installations, which calls for a value not exceeding 21
ohms.
Obviously the lower the resistance of the earth electrode the better.

4.8 Earth Fault Loop Impedance
IEE reg: 612.9 (page 160) Where protective measures are used which require a
knowledge of earth fault loop impedance, the relevant
impedance's shall be measured, or determined by an
alternative method.
Testing for compliance with IEE reg: 411.4.5 (page 48)
Earlier on in the notes we discussed the meaning of Earth Fault Loop impedance and we
saw the reasons for limiting its upper value.
The earth fault loop impedance (Zs) should be determined at the furthest point of each
circuit. This includes socket outlets, lighting points, sub-main cables and other circuits
supplying fixed current using equipment.
Method
Measuring of the earth fault loop impedance (Zs) for circuits incorporating socket outlets
involves no more than plugging in the loop tester and taking a reading. The result obtained
includes the earth fault loop external to the installation (Ze).
For other circuits such as lighting circuits or circuits feeding fixed equipment not connected
via a plug and socket, use will have to be made of a purpose designed set of leads and
probes.
A loop tester which does not trip RCD will need to be used or the value calculated.
With the loop tester, the neutral connection is there only to power the test instrument.
Where a neutral is not available, such as in a 3 phase motor circuit the neutral lead will
need to be conceded to earth along with the earth lead of the tester.

Results
Once we have obtained an earth fault loop impedance reading to what does one compare
it? IEE reg: 411.3.2 (page 46) including table Table 41.1 give the required disconnection
times for TN and TT systems.
IEE Tables 41.2, 41.3, 41.4 and 41.5 (pages 48,49 and 50) of the Wiring regulations give
maximum earth fault loop impedance's for various types and ratings of MCB'S and fuses. It
should be noted that these values are intended as design values only. When a person
responsible for the design of a circuit calculates the maximum earth fault loop or Zs for a
circuit the formula is as follows:
Zs = Ze + (R1+R2)
Where:
Zs = Earth Fault Loop Impedance of the System
Ze = Earth Fault Loop Impedance External to the Installation
RI = Resistance of the line conductor from the origin of the circuit to the furthest point of
utilization.
R2 = Resistance of the protective conductor from the origin of the circuit to the furthest
point of utilization
Under fault conditions the temperature of the conductors will rise until the fault current
reaches a point where the overcurrent protective device operates. To take a account of
this rise in temperature the designer applies a factor to the R1+R2 figure before comparing
his figures with the values shown in IEE Tables 41.2, 41.3, 41.4 and 41.5 (pages 48,49
and 50) . The values for this factor can be found in the 'On Site Guide' published by the
IEE.
Obviously our testing takes place at a temperature far less than the temperature the cable
reaches under fault conditions. To take this into account we would have to apply the same
multiplier as well as to correct the values of R1 and R2 for differing temperature.
Alternatively we could compare our readings with the maximum values detailed in the 'On
Site Guide' , published by the IEE, as the figures contained within this publication have
been adjusted to take the above into account.
Another acceptable method is to divide the reading obtained by our loop tester by a factor
of 0.75. This applies to protective devices listed in the regulations. For protective devices
not listed the factor is 0.66.
i.e.: For a loop tester reading of 1 ohm the adjusted value will be 1 =1.33 ohms
0.75
This value can then be compared directly with tables IEE Tables 41.2, 41.3, 41.4 and 41.5
(pages 48,49 and 50)

Measurement of the External Earth Fault Loop Ze
The Ze or, External Earth Fault Loop impedance, is measured using a phase earth loop
impedance tester at the source of the installation supply. The outgoing supply needs to be
isolated along with the means of earthing, which involves isolating the main bonding
conductor from all other earthing conductors. The reason for isolating the main earth is to
remove the possibility of erroneous readings due to parallel earth paths.
Do Not Forget To Reconnect Bonding

Measurement of Prospective Short Circuit Current
Prospective Short Circuit Current (PSCC) is the current likely to flow in a circuit under fault
conditions. It is the largest current that is likely to flow in a circuit. Protective devices such
as fuses,MCB must be able to break this fault current safely and should be selected in
accordance with the PSCC.
PSCC = Uo
Zt + Z1 + Z 2
where.
Zt = Impedance of transformer winding
Z1 = Impedance of line conductor
Z2 = Impedance of Neutral conductor
U0 = Voltage
By Using a loop tester to measure the line - Neutral loop we can calculate the PSCC.

4.9 Residual Current operates Devices
IEE reg 612.10 (pages 160) Where RCD's are required for additional protection, the
effectiveness of automatic disconnection of supply by RCD's shall be verified using
suitable test equipment according to BS EN 61557-6 (see regulation 612.1) to confirm that
the relevant requirements of Chapter 41 are met.
In order to test the effectiveness of an RCD it is necessary to carry out a series of tests to
confirm that the RCD operates within correct time and current parameters. This sequence
of tests is in addition to using the integral test button incorporated in the RCD. IEE reg
612.13.1 (page 161)
The test is made on the load side of the RCD, between the line conductor and the CPC of
the circuit. The test current is obtained from the live and neutral of the circuit under test.
Any loads connected should be disconnected.
The sequence of tests is:
1)To apply a current equal to 50% of the rated tripping current of the RCD for a period of 2
seconds. The RCD should not trip.
2)Application of a current equal to 100% of the rated tripping current of the RCD. The RCD
should operate within 200mS.
3)Where the RCD is used to provide supplementary protection for basic protection, a test
current of 150 mA is applied for a maximum period of 50 mS. The RCD should operate
within 40 mS.
4)The integral test button incorporated in the RCD is now operated. This checks the
operation of the mechanical parts of the RCD. It does not check the continuity of the
protective conductors or the rest of the earthing system.
The above sequence and results apply to non delayed RCD'S complying with BS 4293. For
time delayed RCD'S the results for test 2 should be within the following range:
50% of rated time delay plus 200mS, and
100% of rated time delay plus 200mS
i.e For an RCD with a delay of 200mS it should trip within a time range of:
( 100 + 200 ) mS = 300mS and
( 200 + 200 ) mS = 400mS

Testing of 3 Phase RCD'S
With certain 3 phase circuits protected by RCD'S a neutral may not be available. As the
RCD tester obtains its test current from the line and neutral of the circuit under test this
poses a problem. We can overcome this by connecting the neutral lead of the tester to
earth. However, it should be noted that the test current will be increased and may trip the
RCD on the 50% test. The RCD should not necessarily be failed in this instance.
Safety
Care must be exercised while carrying out the testing of RCD'S as potentially dangerous
voltages may appear on exposed and extraneous conductive parts when the earth fault
loop impedance approaches the maximum acceptable limit.

4.10 Functional Test Of Switchgear
IEE reg 612.13.2 (page 161)
Assemblies such as switchgear and control gear assemblies, drives controls and
interlocks, shall be subjected to a functional test to show that they are properly
mounted adjusted and installed in accordance with the relevant requirements of these
Regulations.
As a final test the above should be carried out. This would include the switching off and on
of MCB'S etc, to make sure that their mechanical operation is satisfactory.

4.11 Periodic Testing
Periodic testing of an installation should be carried out in the following order:
(a) Continuity of protective conductors and earthed equipotential bonding.
(b) Polarity.
(c) Earth fault loop impedance.
(d) Insulation resistance.
(e) Operation of devices for isolation and switching.
(f) Operation of residual current devices.
Where appropriate, the following tests should also be made:
(g) Continuity of ring circuit conductors.
(h) Earth electrode resistance.
(i) Manual operation of overcurrent protective devices other than fuses.
(j) Electrical separation of circuits.
(k) Protection by non-conducting floors and walls
How much testing needs to be done?
Guidance Note 3 suggests that a random selection of points is tested. This should be equal
to 10% of the installation. If faults were discovered within this batch the batch should be
expanded to 25% and then on to 100% if further faults are discovered.
All socket outlets should be checked for correct polarity.
When checking the continuity of bonding or equipotential bonding conductors the
installation should be isolated from the mains. On no account should bonding conductors
be disconnected with the mains on.

5.1 Certification and Reporting
Chapter 63
Once the initial verification ( this includes both inspection and testing) has been completed
the above regulations call for the issuing of an Electrical Installation Certificate, together
with a schedules of test results. This Certificate should be given to the person ordering the
work. The above mentioned Certificate would be incomplete and void if a schedule of test
results was not included.
Who is responsible for signing the certificate? The Certificate includes space for three
signatures, the person responsible for the Design, the person responsible for the
construction and the person carrying out the Inspection and Test of the installation.
It should be emphasized that the signature for the Inspection and Test section is the
person who actually carries out the Inspection and Test and not someone else who may be
in authority. In some cases all three sections will be signed by the same person. This is
perfectly acceptable.
The Electrical Installation Certificate should not be signed until any defects, which the
person responsible for inspection and test may have identified, have been corrected.
Alterations and Additions
An Electrical Installation Certificate as above or a Minor Electrical Installation Works
certificate , stating the extent of the works covered, shall be issued once the Inspector is
satisfied that the works comply with the Regulations. Any defects found in related parts of
the installation, not effecting the safety of the alteration or addition, should be reported in
writing to the person ordering the work.
If existing defects effect the new work then these defects would have to be corrected
before an Electrical Installation Certificate could be issued and before the new work could
be put into service. An example of this is where bonding or equipotential bonding is
inadequate or omitted as this would seriously effect the safety of the whole installation
including the new work.
The Electrical Installation Certificate should not be used for Periodic Inspections.

Periodic Inspection report
The Periodic Inspection Report form is only to be used for the inspection of an existing
installation. It shall include both inspection and test results.
Again the Extent and Limitations as to the report shall be stated. Recommendations as to
defects and their remedied shall be made.
The report includes a numbering system for this purpose, as follows:
1 Requires Urgent Attention
2 Requires Improvements
3 Requires Further Investigation
4 Does Not Comply With BS 7671:2008 (as amended)
(this does not necessarily imply that the electrical installation is unsafe)
Again, with the Periodic Inspection and Test the main consideration is safety.

Minor Works certificate
Several associations and trade bodies allow the issuing of a 'Minor Works Certificate'. A
minor works is defined as 'work which does not include the provision of a new circuit'
Testing is still essential and the following tests should be carried out to confirm safety.
The Tests are as follows:
1) Circuit impedance R1+R2
2) Insulation Resistance line/Earth
Neutral/Earth
3) Earth Fault loop Impedance
4) Polarity
5) RCD Operation
Included on the form is space to allow the Inspector to comment on the existing installation.

6.1- instrumentation requirements
Continuity Tester
Accuracy +/- 2%
Resolution 0.01 ohms
No Load Voltage 4 - 24v ac or dc
Test Current 200 mA
Insulation Resistance
Accuracy +/- 2%
Test Current 1 mA at the minimum allowable resistance value
i.e 250k for 250v range
500k for 500v range
1M for 1000v range
Other requirements i.e. Must have the capability to discharge capacitance which has
become charged during the test.
Earth Electrode Resistance Tester
Accuracy +/- 2%
Other requirements Facility to check potential and current spikes are within the
testers limits.
Loop Impedance Tester
Accuracy +/-2%
Test Current 20-25A for up to two or four cycles
RCD Testers
Accuracy of test currents + /- 10%
Accuracy of times +/-5%
Time resolution 1mS
Other requirements Able to perform tests for Reg. 713-12
Suitable for RCD ratings of 6,10,30,100 & 500mA
Must apply 150mA test current for no longer than 50mS

International Protection provided by
Enclosures
I.P Ratings
To BS EN 605299

Number Degree of
protection against
ingress of solid
foreign objects
Number Degree of
protection against
ingress of water
0 Not protected 0 Not protected
1 Protected against
access to hazard
parts by back of hand
Protection against
foreign objects of
50mm diameter and
greater.
1 Protection against
vertically falling water
drops
2 Protected against
access to hazard
parts by a finger
Protection against
foreign objects of
12.5mm diameter
and greater.
2 Protection against
vertically falling water
drops when
enclosure tilted at 15º
3 Protection against
tools wires and
others 2.5mm and
greater
3 Protection against
water spraying up to
an angle of 60º on
either vertical side.
4 Protection against
tools wires and
others 1mm and
greater
Protection against
foreign objects of
1mm diameter and
greater.
4 Protection against
water splashing from
any direction.
5 Protection against
tools wires and
others 1mm and
greater
Dust protection
5 Protection against
water jets from any
angle.

Number
Degree of
protection against
ingress of solid
foreign objects
Number
Degree of
protection against
ingress of water
Dust may enter but
not interfere with the
operation of the
device
6 As above 6 Protection against
powerful water jets
from any angle.
No code 7 Protection against
ingress of water
when enclosure is
immersed in water in
standard conditions

Degrees of Protection provided by Enclosures
This was better known as Ingress Protection
IP Code Of Protection. -
This C of P is given in BS EN 60390-2, this document is the standard document, which is
used to form the basic requirements of electrical equipment Standards.
The construction for IP ratings of a specific type of equipment are given in a British
Standard document.
Also in the document are the relevant construction requirements for various plugs and
socket outlets, including ( BS 4343 -- now BS EN 60309-2 ), that is why there is no nation
of this IP classification in BS 7671 .
The degree of protection provided by this enclosure is indicated by two numerals and
followed by an optional letter and /or optional two supplementary letters as follows
IP Coded letters International Protection
First characteristic numeral, (from 0 - 6, or could be letter X, not defined )
Second characteristic numeral, (from 0 - 8 or could be letter X.)
Additional letter (optional ) ; A, B, C, D
Supplementary letter (optional ); H, M, S, W.
the reference could be IP 23CH
Where there is a non specific reference, the numbers can be replaced by the letter X ie. IP
XX , if both the numbers are omitted.
The additional letter / (s) can be omitted without replacement.
Where more than one letter is used then the alphabetical sequence shall apply.

Degrees of Protection provided by enclosures
The ADDITIONAL Letter
Supplementary Letter
In the relevant product standard classification, supplementary information may be indicated
by a supplementary letter following the second characteristic numeral or the additional
letter.
The following letters are currently in use, but extra letters will probably be used as the
standards of various products change.
Product Marking
The requirements for marking a product are specified in the relevant product standard.
For example, IP23CS
The IK code of impact PROTECTION

This IK code of classification was introduced to provide protection for electrical equipment
against mechanical impart.
The code classifies the degree of protection.
Continental countries have their own classification, the IK is now The UK classification,
where there was no previous classification for mechanical impact.
The obvious reason for the introduction of this classification in this country, is that we as a
nation are increasingly selling our products in Europe.
They need to understand our reference with respect to their own.
The standard only describe the general requirements and designations of the system the
application of the system to a specfic enclosure type will be covered by the BS which is
applicable to the enclosure
The IK coding used is marked separately on The equipment from the IP rating.
Coded letters IK Characteristic group 00 to 10
each group represents an impact energy value as shown in the table below

Drip Proof and Splash Proof
Certain electrical equipment has been graded against water ingress by a pictorial
representations which is now superseded by the IP rating, nevertheless these should be
able to be identified and recognized and understood.
The comparisons between the differing references are not exact, but the installer, designer
and the tester of such equipment must be able to recognize the seals used, so that the
equipment being used is suitable for the location of use.

Choice of Protective Devices
The selection of protective devices depends upon :
l . prospective fault current
2. circuit load characteristics
3. cable current – carrying characteristics
4. disconnection time limit.
Show circuit capacities of the protective devices Device type
Device Short-circuit Device Spec Short Circuit Capacity kA
Semi-enclosed fuse to BS 3036 S1A 1
S2A 2
S4A 4
Cartridge fuse to BS 1361 16.5
33.0
General purpose fuse to BS 88 50 @ 400v
16.5 @ 230v
80 @ 400v
Circuit breakers to BS 3871 M1 1
M1.5 1.5
M3 3.0
M4.5 4.5
M6 6.0
M9 9.0
Icn Ics
Circuit Breakers to BS EN 60898 1.5 (1.5)
3.0 (3.0)
6.0 (6.0)
10 (7.5)
15 (7.5)
25 (10)
Icn = rated ultimate S / C capacity.; Icn > Ipsc , except where it is used as back-up
protection ref To manufactures information
lcs = This is the max level of fault current operation after which further service is assumed
without loss of performance Protective devices must cater for both: -protection
against overload/ short circuit protection

safety in inspection and test

2011-07-12T06:08:00.000-07:00

General guidance
Safety in electrical testing at work
What is this
guidance about?
This booklet provides basic guidance on safe
electrical testing and is intended for anyone who
runs or manages a workplace where electrical
testing is carried out, and for those people doing
the actual testing. It is complemented by
information sheets which give more detailed
information about specific types of testing.1–4
Electrical testing may be carried out for a
number of reasons, for example:
(a) quality assurance tests on electrical
components;
(b) diagnostic testing;
(c) fault-finding on electrical plant;
(d) routine safety checks.
The guidance contains recommendations to
help you prevent or reduce electrical danger.
Some of the main ways in which this can be
done include:
(a) following safe systems of work, for example:
(i) taking precautions to prevent people
who are not doing the testing coming
into contact with exposed live parts;
(ii) taking precautions to prevent the testers
coming into accidental contact with
exposed live parts;
(iii)protecting and insulating both the
equipment being worked on and the
testing equipment.
(b) using test equipment that is suitable for the job;
(c) making sure that people doing the work are
suitably trained and experienced so that they
understand safe working practices and the
equipment on which they will be working.
What types of
testing are covered?
This guidance covers electrical testing in
situations (mostly low voltage, ie not exceeding
1000 V ac or 1500 V dc) where equipment like
domestic appliances is being tested. Most of this
equipment will be used on mains supply
voltages of 230 V ac single phase and 400 V ac
three phase. However, there could be internally
derived voltages which are much higher and in
some cases above the low voltage limits.
Some of the test voltages applied to equipment
during testing may be above the low voltage
limits. These voltages are not considered
dangerous if the maximum output current
available from the test instrument is reliably
limited to no more 5 mA (traditionally 5 mA ac
has been used, but since May 20015 new
equipment should be limited to 3 mA ac).
2
Safety in electrical testing at work
What is the risk of
injury?
Injury can occur when live electrical parts are
exposed and can be touched, or when metalwork
which is meant to be earthed becomes live at a
dangerous voltage. The likelihood of touching
live parts is increased during electrical testing and
fault-finding, when conductors at dangerous
voltages are often exposed. This risk can be
minimised if testing is done while the equipment
is isolated from any dangerous source of supply,
although this cannot always be done, and care
must also be taken to prevent contact with any
hazardous internally produced voltages.
The most dangerous injuries are those caused
by electric shock. This is because the effects of
a shock are largely unpredictable and can easily
lead to a fatal injury. However, there is also a
risk of burn injuries resulting from arcing when
conductors are accidentally short-circuited. A
secondary risk can be the harm caused by a
person reacting to an electrical injury, for
example by falling or being traumatised by
the experience.
Electric shocks occur when contact with a live
conductor causes sufficient current to pass
through the body to cause an injury. As a rough
guide, voltages exceeding 50 V ac or 120 V
ripple free dc should be considered hazardous
in a dry, unconfined, non-conductive location.
These voltage values must be reduced if the
location is wet, confined or conductive, so
where there is an adverse environment, those in
charge of the work and those doing the work
should be aware of the probable increase in
injury risk.
In some equipment, for example microwave
ovens, high voltages of several thousand volts
are used and there is a very high risk of fatal
injury if the exposed conductors are touched at
these voltages. Injury may also be caused by
currents as low as 5 mA or by stored charges.
Suitable precautions must be taken to prevent
contact with stored charges in excess of 350 mJ.
If the skin is pricked or cut at the point of contact,
the shock current (and hence the seriousness of
the injury) will be higher. Healthy skin may also
become damaged at the time of contact either by
the burning effect of the current or by penetration
from sharp-ended conductors.
Carrying out a risk
assessment
As well as the level of voltage, charge or
current and the nature of the environment,
there are a number of other factors that need
to be considered when you are assessing the
risk of injury arising from electrical testing
work. A risk assessment should be carried out
before testing begins, to help you identify the
precautions you need to take.
Some questions to ask when carrying out the
risk assessment are:
(a) Can the work be done with the equipment
dead or energised at a safe voltage or current?
(b) Is it absolutely necessary for someone to be
working on or near to equipment that is live
at dangerous voltages or current levels?
(c) What is the maximum voltage on
conductors that will be exposed during the
work activity?
(d) Are the testers competent? Are they
adequately trained and knowledgeable to do
the particular work and ensure that others
are not put at risk?
(e) If testers are not considered fully competent,
are they adequately supervised?
(f) What physical safeguards should be applied to
the equipment under test to prevent injury, eg
the use of temporary or permanent screens?
(g) Is the test instrumentation of safe design?
Has it been properly maintained?
(h) Is it necessary to set up a permanent test
area separate from the rest of the workplace,
3
Safety in electrical testing at work
where equipment can be taken for testing? Is
it necessary to set up a temporary test area
around the equipment?
(i) Are the testers able to supervise the working
area sufficiently and at all times to prevent
danger to others?
(j) Where testing is part of an ‘after sales service’
how much must be done at customers’
premises? If testing is being done in a
customer’s home, what special precautions
are required to protect the tester and others?
(k) To what extent should the testers be
supervised or accompanied?
(l) If the testers design, manufacture or use any
special test equipment, does it meet BS EN
61010-1?6
(m) How big is the unit under test and how
much space is required around it to undertake
the testing in a safe and unconfined
manner?
(n) Are all the other workshop employees competent
to avoid danger if there is a need for
them to approach the equipment? If not, how
can you make sure that they do not do so?
(o) Will the equipment be left unattended while
live, for example while being ‘soak tested’?
(p) Does the workbench or separate area
require a warning, eg a light, to show that
testing is in progress?
(q) Is there a need for additional emergency
switching devices for use by other employees
to reduce the degree of injury to testers?
Can residual current devices (RCDs) be used
to provide supplementary protection? (NB:
This guidance and the complementary
information sheets1–4 refer to RCDs or
30 mA RCDs. See the section relating to
residual current devices on page 9 for a
fuller explanation.)
(r) Is it possible to reduce the number of available
paths to earth to reduce the likelihood of a
phase-to-earth shock, eg by the use of barriers,
screens and insulating mats?
(s) Is it possible to use unreferenced supplies, eg
isolating transformers/batteries to reduce the
likelihood of a phase-to-earth shock?
Managing electrical
testing
You must provide a safe working environment
and establish a safe system of work for your
employees. The results of your risk assessment
will help to identify the steps you need to take
to do this. Employees must co-operate and take
reasonable care for their own and other
people’s safety while they are at work. The
following advice needs to be considered for all
activities involving testing.
Personnel
All personnel must:
(a) understand that the risk of electric shock
injury will still remain during the testing
process, even with the use of earth-free test
areas and/or isolating transformers and/or
RCDs;
(b) fully understand the scenarios in which these
electric shock injury risks can arise in the
particular workplace(s);
(c) be given adequate first-aid training,
including cardiac pulmonary resuscitation
(CPR) skills.
Permanent test areas
These areas must:
(a) be under the control of a responsible person;
(b) be in an area set apart by barriers to prevent
entry;
(c) have suitable warnings provided at the
entrance;
(d) be accessible during testing only to
authorised staff or people working under
their direct supervision;
(e) have suitable warning lights indicating
that testing is in progress and other
warning lights to indicate when it is safe
to enter the area (duplicate red and green
lights are often used);
(f) have emergency-stop push buttons or
equally effective means to cut all test
4
Safety in electrical testing at work
supplies in the event of emergency. These
emergency controls should be prominently
identified. (NB: The emergency controls
should not remove supplies to the general
lighting in the area.)
(g) display an electric shock poster, eg Electric
shock: First-aid procedures,7 at prominent
locations, showing emergency arrangements,
especially telephone numbers;
(h) have good housekeeping arrangements,
including adequate clear working space.
Temporary test areas
In some situations it may not be practicable or
desirable to remove equipment to a permanent
test area, eg because the equipment is too large
for the test bay or is located at the customer’s
premises. If live testing needs to be carried out,
a temporary test area should be set up around
the equipment. When setting up a temporary
test area, all the precautions listed above for
permanent test areas should be taken, unless
it is not practicable to do so, in which case
an assessment needs to be made of what
precautions are needed to reduce that risk to
as low a level as possible.
Remember that simple ‘Go/No go’ plug-in
testers will in general only provide a polarity
check and an indication that an earth may be
present, but not its effectiveness.
Earth-free areas:
Make a test area as earth free as possible, in
conjunction with the use of isolated supplies. To
achieve this, take the following precautions:
(a) use a test bench made of insulating material
with shrouded legs and framework to
prevent the possibility of contact with earth
while testing;
(b) remove all pipes, radiators, structural
steelwork, metal conduits, earthed electrical
appliances, metallic socket outlets etc from
within reach of the test bench, or
permanently shroud them with insulating
material to prevent contact;
(c) where soldering irons and task lighting are
needed, they should be extra low voltage,
supplied from an isolating transformer
complying with BS 615588 to prevent the
need for earthed metal at the test area;
(d) if a television or radio aerial socket is needed
at the test area, this should be of isolated
construction complying with BS 415;9
(e) insulating rubber matting complying with
BS 92110 should be provided on the floor,
kept clean and dry, and regularly tested, and
should be large enough for the test operative
to remain on it whether standing or seated
during testing (NB: Chair legs may damage
the matting.);
(f) if electrostatic discharge wrist straps are
provided, these must incorporate a suitable
resistance (say 1 Megohm or more). The use
of a wrist strap which directly connects the
wearer to earth is not permissible. For further
advice see BS IEC 61340-5-1: 1998.11
Supplies to equipment under
test
Each item of equipment under test should be
provided with its own test supply. These supplies
should be from designated sockets or terminals
5
Safety in electrical testing at work
provided with covers interlocked with the supply
isolator. The supplies should have suitable system
protection against overload and overcurrent in
the event of faults, eg fuses. Note that:
(a) where an isolating transformer is used for the
supply to the equipment under test this
should comply with BS 615588 and a
separate transformer should be used at every
test bench. If this is not reasonably practicable,
the same isolating transformer may be used
for supplies to alternate benches, provided
the risk of referencing this supply to earth at
any bench is properly controlled and the
transformer does not then have an
unacceptably high leakage current;
(b) the supply from the isolating transformer
should be provided from a single socket
outlet and clearly marked ‘only for use for
making live equipment under test’. No fixed
wiring should be connected to the earth
terminal of the outlet socket. The face plate
of the socket should be made of insulating
material. There must be no unnecessarily
exposed live parts on equipment under test;
(c) in certain circumstances Class I equipment
under test must be effectively earthed unless
supplied via an isolating transformer. This
will bring with it an increased risk of electric
shock which may be minimised by the use of
other precautions.
(d) when the equipment under test is Class I,
any pre-existing earth fault must be detected
and corrected before making the equipment
live. In the case of the supply from an
isolating transformer, failure to do this will
mean that there may be a hazardous shock
risk in the event of a simultaneous contact
between the enclosure of the equipment and
one or both poles of the isolated test supply;
(e) the integrity of the circuit protective
conductor (earth) of all portable/transportable
Class I equipment must be re-tested after all
test-bench work has been completed, to
ensure that no earth faults are present before
the equipment is used again on a normal
mains supply.
Risk assessment – test
equipment and electricity
supplies
All measures used to control risk of electric
shock should follow the hierarchy given below:
(a) first and foremost, control as many of the
risks as possible by hardware methods;
(b) secondly, control all other foreseeable risks
by the use of safe systems of work. These
must be made known to and fully
understood by all staff involved, regularly
monitored, and recorded in written form
(for reference and to permit refinement or
amendment as and when needed); and
(c) finally, use of competent staff who must
possess the necessary level of technical
knowledge and experience (or be
supervised by a competent person) to
prevent risk of injury.
If the hardware precautions resulting from the
risk assessment include the provision of isolating
transformers for the source of supply to mainspowered
test equipment, then such provision
should normally be made and the isolation
transformer should be separate from the
equipment under test. An instrument shelf
should be provided for that equipment.
Some of the risks associated with the use of test
equipment can be reduced, but not eliminated by
placing all test equipment on an insulated shelf
immediately above the test bench. This will reduce
the chance of simultaneous contact between the
test equipment and the equipment under test.
When the hardware precautions resulting from
the risk assessment do not include the provision
of isolated supplies to the mains-powered test
equipment, all supplies to test equipment should
be protected by 30 mA RCDs. NB: For supplies
in excess of 16 A to equipment under test or
where the equipment under test has a high
leakage current it may not be practicable to use
an RCD because of nuisance tripping. For
further advice see Section 607 BS 7671.12
6
Safety in electrical testing at work
Setting up safe test
areas
It is important to make sure that anyone not
involved with electrical testing work is kept free
from risk. This can be done by confining testing
work to a designated test area. In some
workshops, it might be possible to set up a
permanent workbench and test area, to which
only the testers have access. Otherwise,
unauthorised people should be prevented from
approaching the equipment under test by
physical barriers or other demarcation methods
which form part of the test area boundary.
A test area can be:
(a) a designated room built as a test area with
special protection features and fitted with
secure doors (possibly interlocked,
depending upon the degree of risk) to
prevent unauthorised access;
(b) an area set aside in a workshop with some
form of permanent barrier as a demarcation;
(c) a work bench which might be designed as a
test bench or be used for repairs and testing;
(d) a designated work position within, or at the
end of, a production line;
(e) a temporary area set up around equipment
using purpose-built barriers as demarcation;
(f) an area around fixed equipment, such as
switchgear, or control gear, where skilled
people are carrying out repairs, fault-finding
or testing during maintenance work.
In workshops where all employees have been
adequately trained and instructed in safety
practices and all unauthorised personnel are
effectively excluded, local demarcation of the
workbench or work area where testing is
done may not be necessary. All employees
need to be aware that those who are carrying
out testing should not be distracted by the
interference of others who are not involved
with the test in progress.
Protecting the people
doing the testing
The measures that are used to protect the
people doing the testing need to be effective to
prevent them coming into accidental contact
with dangerous exposed conductors. This might
be either a single-hand contact with a source of
energy which has one of its supply conductors
7
Safety in electrical testing at work
connected to earth, or another area of
conducting surface.
Class I equipment is in this category because the
mains at source are earth referenced; so is
electronic equipment where a large metal
surface (or chassis) is connected to the source.
There is also a risk of injury from sources of
supply which are not earth referenced and
where accidental simultaneous contact with
both poles of the supply is possible.
Methods of reducing the risk of a shock from
simultaneous contact with conductors include:
(a) testing at reduced, non-hazardous voltages
and currents;
(b) using interlocked test enclosures in which
the unit under test is contained;
(c) using temporary insulation;
(d) replacing covers which need not be removed
for the purposes of the test, for example
once supply connections have been made;
(e) creating an area which is as earth free as
practicable;
(f) using isolating transformers connected to the
mains supply;
(g) using 30 mA RCDs.
The following sections provide more detail
about each of these protective measures.
Safe voltages and currents
It may be possible to test the equipment by
energising it with non-hazardous voltages and
current levels. This should always be considered
as the first option before deciding to use
dangerous voltages and current levels.
Interlocked enclosures
These can vary in size from a small benchmounted
box with an interlocked hinged lid to
a large enclosure (large enough for people to
enter) equipped with access gates which are
secured by interlocks. It is important to ensure
that the safety performance of the interlocking
system is comparable with that of a switching
device used for isolation purposes. The use of a
trapped key (key exchange) system interlocked
with the access and the isolator can assist. In
general, interlocking using the control system
alone is not acceptable; the power supply
should be isolated by the interlock system.
In certain circumstances there may be the
potential for a stored charge to occur, eg from
the use of capacitors. In these circumstances the
supply to the equipment under test should be
earthed, preferably automatically, before entry is
made. If it is not possible to earth the
equipment automatically, it should be manually
earthed by the use of a suitably insulated
earthing tool. Where automatic earthing is used,
it is essential to use, in addition, a manual
earthing device before making contact with any
parts that have previously been made live.
Where large enclosures are used, you must
make sure that people cannot be inside the
enclosure while there is danger from the
equipment being tested.
8
Safety in electrical testing at work
Temporary insulation
Where there is risk from simultaneous contact
with hazardous conductors, do not assume that
employees will be able to avoid accidental
contact. Consider using temporary insulation
which may be in the form of purpose-made
screens or insulating sheets or shrouding (rigid
or flexible). However, there may be a practical
limit on the use of screens when testing
compact electronic assemblies.
Earth-free areas
It is difficult to achieve a true earth-free area,
since there is a need to ensure that floors and
walls will not conduct current which can give
rise to shock injury. Suitable insulating materials,
including mats, are therefore needed to
construct an earth-free area. These parts will
then have to be tested at regular intervals to
demonstrate that their insulation properties are
being maintained.
An area which is as earth free as practicable can
be more easily created, but a thorough risk
assessment needs to be done to ensure that the
testers will not make accidental contact with
any earthed conductors. Items such as heating
and water pipes and radiators should be
enclosed, or the test area should be situated to
prevent simultaneous contact by the tester with
the item under test and the earthed item. Earthfree
areas should have the minimum of
exposure of conductive parts. A 30 mA RCD
could be used as supplementary protection.
Earth-free areas are often used in conjunction
with isolating transformers.
Where it is not possible to make an area earth
free because it is necessary for the test
equipment and/or the equipment under test to
be earthed, it is still possible to reduce the
extent of the accessible earthed metalwork.
Isolating transformers
Isolating transformers connected in the test
supply will prevent the risk of electric shock
if a person touches a single live conductor of
the isolated supply while in contact with an
earthed conductor.
It should be clearly understood, however, that
an isolating transformer cannot prevent an
electric shock if someone makes contact
simultaneously with both conductors of the
supply on the secondary side of the transformer,
unless the output voltage is below 50 V ac (120
V dc) in dry conditions and 16 V ac (35 V dc)
in wet conditions.13
The integrity of the isolation from earth should
be tested regularly, or earth fault monitoring
devices should be installed, to ensure that
dangerous earth faults are detected.
Residual current devices
(RCDs)
These are supplementary protection devices
which do not prevent an electric shock, but are
able to limit the duration of some shocks by
being able to cause rapid disconnection of the
electricity supply in the event of a relatively low
current flowing to earth, such as may occur
during an electric shock. They are, therefore,
able to provide a much higher level of
protection against the risk of a severe electric
shock than could be provided from an
unprotected source.
An RCD required to minimise the risk of
personal injury should have a rated tripping
current of no more than 30 mA and should
not have an adjustable time delay. Although the
30 mA versions are often used, those with lower
rated tripping currents (typically, 10 mA or
below) are readily available and may be used to
provide additional protection where nuisance
tripping is not a problem.
Where personal safety depends in part upon the
operation of an RCD, the RCD must be tested
using the built-in test facility at appropriate
intervals (eg portable RCDs before each use,
fixed RCDs weekly). In addition, all RCDs
9
Safety in electrical testing at work
should be tested at least annually using an RCD
tester which will check the tripping current and
the speed of operation.
Test equipment
Where possible, test equipment should be of a
proprietary design. In this case the manufacturer
should have taken account of its safety performance
during use. Where applicable, test
equipment should be manufactured to BS EN
61010.6
Purpose-built test equipment must be designed
and constructed to the same standards of safety
as proprietary equipment. Where equipment is
mains powered, it must be safe to use as a piece
of electrical equipment in its own right. In
addition, the arrangements for connecting it to
the equipment under test must be safe.
Insulation test instruments can generate high
voltages at their output and some have an
option to limit the output current to a safe level.
The generally accepted safe limited current is
5 mA (traditionally 5 mA ac has been used, but
since May 2001 new equipment should be
limited to 3 mA ac5). If accidental contact with
the output conductors occurs, the risk of injury
will be minimised if these current levels are not
exceeded. If higher current levels are necessary,
special precautions need to be put in place to
prevent injury. These include using test probes
fitted with control switches, or using interlocked
enclosures to prevent access to the dangerous
parts, and restricting the testing work to
authorised people. The majority of insulation
testing can be done within the safe current
limits specified above.
The connecting leads of test equipment must be
of a design that provides adequate protection
from electric shock. The only exception to this
is when test lead connections are inside an
interlocked enclosure and are connected to and
disconnected from the equipment under test,
while the source of supply is isolated and
measures taken to ensure that any stored energy
is dissipated. In this case, the connecting lead
conductors become an extension of the
conductors being tested and so present the
same risk of injury.
Test instruments
The following paragraphs apply mainly to
oscilloscopes but can sometimes apply to other
instruments, eg signal generators.
Hazardous voltages may arise on the enclosures
of Class I (earthed) oscilloscopes, or, in some
cases, on certain types of double-insulated,
Class II oscilloscopes. The hazardous voltages
may arise from the voltages being measured on
the equipment under test, or in some cases,
from the breakdown of the insulation of the
oscilloscope itself. The measurement problems
arise because most oscilloscopes have the ‘signal
common’ terminals connected to the
oscilloscope’s chassis and hence its enclosure
and connectors. In a Class I oscilloscope these
parts are connected to the supply protective
conductor. This means that all measurements
must be made to earth which limits the
10
Safety in electrical testing at work
measurements that can be made by the
oscilloscope. A technique has been developed to
‘float’ the oscilloscope (ie remove the
connection to the supply protective conductor)
which then allows the oscilloscope’s enclosure
to float above earth potential (which could be at
high voltages for some types of measurement)
with obvious possible shock risks. Operation of
an oscilloscope with the protective conductor
removed means that it is no longer protected
against internal insulation breakdown. Another
disadvantage with this situation is that it will
then be necessary to attempt to create an earthfree
area. Such use also defeats the equipment
manufacturer’s primary protection concept for
Class I protection and should be discouraged.
A number of methods have been developed to
allow floating measurements to be made more
safely. One method is to supply the oscilloscope
via an isolation transformer, so removing the
earth reference in the supply and allowing
floating measurements. The advantage of this
method was that an earth-free area is not
required but the disadvantage is that the
oscilloscope is not protected against internal
insulation breakdown to the chassis. (The
oscilloscope’s internal insulation could be
over-stressed if high-voltage measurements
are being taken.)
A second method is to use a proprietary isolation
monitor (sometimes called a line isolation
monitor or an earth (ground) isolation monitor)
in the supply to the oscilloscope. This allows the
oscilloscope to operate with its protective
conductor disconnected but the monitor
continuously checks the voltage between the
oscilloscope’s enclosure and the supply earth. If
the oscilloscope’s enclosure reaches a hazardous
voltage, the monitor removes the mains supply
to the oscilloscope and usually reconnects the
supply protective conductor. A typical
operational setting for a monitor would be about
30 volts RMS. The oscilloscope would still be
protected against internal insulation breakdown.
The disadvantage is that it can only be used to
measure low-level signals because the
oscilloscope’s internal insulation could otherwise
be over-stressed.
In recent years, developments have led to
various devices that can be used in an
oscilloscope’s measuring probes which allow
the Class I oscilloscope to be earthed to the
mains supply, but which isolate the measured
voltages to prevent them appearing on the
oscilloscope’s enclosure. Modern proprietary
devices use various techniques to achieve
isolation (eg opto-isolators) and typically
allow measurements to be made ranging from
millivolts to thousands of volts. Bearing in
mind the risks involved, such isolators should
be regarded as being reasonably practicable
safeguards. The isolation devices come in
several forms and may have slightly different
names, according to the manufacturer. Some
of the common names for these devices are:
isolation amplifiers; differential amplifiers;
and isolation probes. Correct selection of
device, according to the measurements to be
made, is important. The user should seek the
manufacturer’s advice.
Some manufacturers now offer oscilloscopes
with isolated inputs (ie where the measured
inputs are isolated from each other and from
the oscilloscope’s chassis), up to reasonably high
voltage levels (typically 850 V peak ac and dc).
Consideration should be given to the use of
these as well as to all-insulated, Class II
oscilloscopes. Battery-operated oscilloscopes
which can be used up to reasonably highvoltage
measurement levels are available. These
are not referenced to earth.
It is good practice to include an RCD with a
rated tripping current of, at most, 30 mA in the
power supplies to Class I instruments, soldering
irons and any other mains-powered equipment.
If isolation transformers are used to supply
power to fixed socket outlets as part of a
11
Safety in electrical testing at work
distribution system for test supplies, the sockets
should be of a different type to standard
sockets, or of the polarised type, to ensure they
are only used for the purpose intended.
Safe systems of
work
Details of safe systems of work for testing
activities should, wherever it is reasonably
practicable to do so, be written down. In order to
produce a workable system, all personnel should
be involved in the preparation of the safe systems
of work. The completed documents, which will
need to be reviewed from time to time, should be
made readily available to employees.
Where testing is confined to diagnostic testing
on electrical distribution systems and equipment
(eg switchgear), by electrically competent
persons, the contents of the written documents
should cover the essential safe working
practices. They may not need to cover the
inherent background knowledge of such a
competent person (this will of course depend on
the experience of the competent person).
Test personnel who work in customers’
premises might have to work under different
rules, as compared to working at a factorybased
test facility. This means that there may
need to be two sets of rules. This should be
taken into account when producing the safe
system of work.
The contents of the written safe systems of
work should include, as a minimum, details of:
(a) who is authorised to undertake testing and,
where appropriate, how to access a test area
and who should not enter the area;
(b) where temporary test areas are constructed,
how this is to be done;
(c) rules for isolating equipment and how the
isolation is secured;
(d) the correct use of additional protection
measures, for example flexible insulation, that
have to be applied to the equipment under
test while its covers are removed. If it is
considered necessary to apply the insulation
and remove covers while the equipment is
live, this risk should also be assessed;
(e) what form of power supply should be used
to energise the equipment under test,
particularly where use of the wrong method
would compromise safety;
(f) what is expected of test personnel regarding
the inspection of test equipment before use,
and how defects are to be reported;
(g) the correct use of any warning devices that
form part of the safety system at designated
test areas;
(h) instructions about what action should be
taken in an emergency situation.
Training
All personnel involved in testing should be
given specific safety training relevant to the
work they are doing. Appropriate training or
instruction must also be given to anyone who
may attempt to enter test areas and approach
test benches.
New training is likely to be necessary whenever
any of the following occur:
(a) changes to product design, layout and
installation;
(b) changes to production or working methods;
(c) changes to test methods and instruments;
(d) changes to test personnel and others who
may be affected.
Competence of
testers
In small businesses, skilled electricians or
technicians are sometimes employed to look
after the day-to-day operation of the electrical
systems. If such people are involved in setting up
testing arrangements, make sure that they are
12
Safety in electrical testing at work
aware of all aspects of safety relating to testing.
Specialist competent advice may be needed to
ensure that the testing procedure is safe.
When setting up a testing area, it is important
that people who are electrically unskilled or
inexperienced are protected from electrical
danger at all times. Appropriate precautions will
also need to be taken to prevent injury of people
who have electrical knowledge and skills.
Remember that even a skilled person can make
accidental contact with dangerous electrical
conductors if they are not protected. Someone’s
personal electrical competence should not be
relied on as their main protective measure.
The precautions that are taken should be
reviewed regularly, to make sure that they are
being followed and are still appropriate for the
work that is being done. As part of this safety
review, employees should be given sufficient
instruction and training on how the safe working
procedures have been amended. This is especially
important where there is a change in design of
products being tested which is relevant to how
the protection concepts are applied.
It is good practice to give one person the task of
reviewing designs and implementing any
changes to safety procedures that are necessary
following discussions with the test personnel. A
safety review should be carried out when
changes are made that may affect testing work,
such as changes in production methods, supply
arrangements, test methods and instruments, or
when personnel changes are made.
Where testing is done by a contractor invited to
a site, safe working arrangements must be
discussed and agreed before the work starts,
preferably at the contract discussion stage. This
enables everyone concerned to know who is
doing what and who is responsible for what, so
that the work can be done safely and without
risk to the contractor’s employees, the site
employees and others who might be affected. In
particular, the person who is responsible for the
safe isolation and state of the equipment should
be identified and agreed.
Legal requirements
The Electricity at Work Regulations 1989 are
the principal legislation relating to electrical
testing activities. Regulation 4(3) requires that
‘work on or near to an electrical system shall be
carried out in such a manner as not to give rise,
so far as is reasonably practicable, to danger’.
Regulation 14 places a strict prohibition on
working on or near live conductors unless:
(a) it is unreasonable for the equipment to be
dead;
(b) it is reasonable for the work to take place on
or near the live conductor; and
(c) suitable precautions have been taken to
prevent injury.
In addition, employers are required under
regulation 3 of the Management of Health
and Safety at Work Regulations 1999 to
assess the risks to the health and safety of
their employees while they are at work, in
order to identify and implement the
necessary precautions to ensure safety.
13
Safety in electrical testing at work
References
1 Safety in electrical testing: Servicing and
repair of domestic appliances Engineering
Information Sheet EIS35 HSE Books 2002
2 Safety in electrical testing: Servicing and
repair of audio, TV and computer equipment
Engineering Information Sheet EIS36
HSE Books 2002
3 Safety in electrical testing: Switchgear and
control gear Engineering Information Sheet
EIS37 HSE Books 2002
4 Safety in electrical testing: Products on
production lines Engineering Information
Sheet EIS38 HSE Books 2002
5 BS EN 50191: 2001 Erection and operation
of electrical test equipment
6 BS EN 61010-1: 1993 Safety requirements
for electrical equipment for measurement,
control and laboratory use (full document is
in 11 parts)
7 Electric shock: First-aid procedures
HSE Books 2002 ISBN 0 7176 2264 9
8 BS EN 61558-1, -2-1, -2-2, -2-4, -2-6:1998
Safety of power transformers, power supply
units and similar. Particular requirements for
safety isolating transformers for general use
9 BS 415: 1990 Specification for safety
requirements for mains-operated electronic
and related apparatus for household and
similar general use
10 BS 921: 1976 Specification. Rubber mats for
electrical purposes
11 BS IEC 61340-5-1: 1998 Electrostatics:
Protection of electronic devices from electrostatic
phenomena. General requirements
12 BS 7671: 2001 Requirements for electrical
installations (IEE Wiring Regulations.
Sixteenth edition)
13 BS PD 6536: 1992 Extra-low voltage (ELV)
limit values
Further reading
HSE publications
Memorandum of guidance on the Electricity at
Work Regulations 1989. Guidance on
Regulations HSR25
HSE Books 1989 ISBN 0 7176 1602 9
Safe use of work equipment. Provision and Use of
Work Equipment Regulations 1998. Approved
Code of Practice and guidance L22 (Second
edition) HSE Books 1998 ISBN 0 7176 1626 6
Management of health and safety at work.
Management of Health and safety at work
Regulations 1999. Approved Code of Practice
and guidance L21 (Second edition)
HSE Books 1999 ISBN 0 7176 2488 9
Maintaining portable and transportable
electrical equipment HSG107 1994
ISBN 0 7176 0715 1
14
Safety in electrical testing at work
Electrical test equipment for use by electricians
GS38 1995 ISBN 0 7176 0845 X
Electricity at work: Safe working practices
HSG85 ISBN 0 7176 0442 X
Other publications
A design guide for the electrical safety of
instruments, instrument/control panels and
control systems (Ref 178) Engineering
Equipment and Material Users’ Association
(EEMUA), 14-51 Belgrave Square, London
SW1X 8PS Tel: 020 7496 8990
ISBN 0 85931 080 9
DASA Quality criteria (Section 2 ‘Competence’
and 3.1 ‘Electrical Safety Tests’) Domestic
Appliance Service Association (DASA), 6-9 The
Maltings, Stanstead Abbotts, Herts SG12 8HG
Tel: 01920 870173 (free)
Electrical maintenance: Code of practice The
Institution of Electrical Engineers (IEE), Savoy
Place, London WC2 R0BL Tel: 020 7240 1871
ISBN 0 8529 6769 1
British and international
standards
BS EN 61557-1:1997, IEC 6155-1:1997
Electrical safety in low voltage distribution
systems up to 1000 V ac and 1500 V dc:
Equipment for testing, measuring or monitoring
of protective measures. General requirements
(full document is in nine parts)
BS 3535-2:1990 Isolating transformers and
safety isolating transformers. Specification for
transformers for reduced system voltage.
BS PD 6519 Guide to the effects of current on
human beings and livestock. Part 1: General
aspects - Guidance on the effects of ac
(frequencies between 15 and 100 Hz) and dc.
Part 2: Special aspects relating to human beings -
Guidance on the effects of alternating current
and frequencies above 100 Hz, with special
waveforms, or in the form of short duration
unidirectional single impulses. Part 3: Effects of
current passing through the body of livestock.
Addresses of trade
and professional
associations
Radio, Electrical and Television Retailers’
Association (RETRA),
RETRA House, St. John’s Terrace, 1 Ampthill
Street, Bedford MK42 9EY
Tel: 01234 269110
Engineering Equipment and Material Users’
Association (EEMUA),
45 Beech Street, London EC2Y 8AD
Tel: 020 7496 8990
British Electrotechnical and Allied
Manufacturers’ Association (BREAMA)
Federation of the Electronics Industry (FEI)
Russell Square House, 10/12 Russell Square,
London WC1B 5EE
Tel: 020 7331 2000
Domestic Appliance Service Association
(DASA),
69 The Maltings, Stanstead Abbotts,
Hertfordshire SG12 8HG
Tel: 01920 870173
Association of Manufacturers of Domestic
Electrical Appliances (AMDEA)
Rapier House
40-46 Lambs Conduit Street
London WC1N 3NW
Tel: 020 7405 0666
Institution of Electrical Engineers (IEE),
Savoy Place, London WC2 R0BL
Tel: 020 7240 1871
15
While every effort has been made to ensure the accuracy of the references listed in this publication,
their future availability cannot be guaranteed.
16

safety for domestic appliances

2011-07-12T06:03:00.000-07:00

What is this guidance about?
This information sheet contains specific advice about
some of the ways of avoiding injury during the servicing
and repair of domestic appliances such as washing
machines, dryers, refrigerators/freezers, cooking
equipment etc, normally operating from a 230 volt
supply. Audio, TV and computer equipment are dealt
with in Safety in electrical testing: Servicing and repair
of audio, TV and computer equipment.1 Further advice is
given Safety in electrical testing at work: General
guidance 2 and other guidance on electrical safety (listed
under ‘Where can I get more information?’ on page 3).
How can injuries happen during testing?
The most significant danger to people carrying out
electrical testing work is that they might suffer an electric
shock. Any simultaneous contact of a part of the body
with a conductor that is live at a dangerous voltage, eg
one that is connected to the mains supply while another
part of the body is connected to an earth, will result in an
electric shock. There is also a risk of burn injuries
resulting from arcing when conductors are accidentally
short-circuited.
An electric shock can lead to serious injury, sometimes
fatal. Injuries can also occur when a person reacts to an
electric shock, for example by falling or touching another
hazard. Factors which are likely to increase the risk of
receiving an electric shock include the following:
(a) The majority of domestic appliances have large
areas of earthed metal that may be easily touched.
Touching exposed live conductors connected to the
mains supply at the same time as touching the
earthed metalwork will result in an electric shock;
(b) Some appliances could also be using water in their
operation, such as washing machines or
dishwashers. This may lead to an increased risk of
shock because water can conduct electricity and
reduces the resistance of the skin;
(c) When working on microwave ovens there may be a
risk of severe electric shock from the internally
generated high voltage (approximately 4kV);
(d) Work may be carried out in the customer’s home,
so people other than those doing the work
(including children) may also be at risk;
(e) Additional risks may be present at the customer’s
premises if their electrical installation is not
electrically sound, eg earthing, insulation
resistance, polarity.
Carrying out a risk assessment
To help you identify the precautions that are necessary
for carrying out electrical testing work safely, you need to
do an assessment of the risk of injury posed by the work
being done. When assessing the risk, you need to think
about the hazards that are present, who may be harmed
and how, and the effectiveness of existing precautions.
Bear in mind the examples of factors given in this
guidance which might increase the risk.
When carrying out a risk assessment for electrical
testing, ask yourself the following questions:
(a) Can the work be done with the appliance dead?
(Repairs and replacements of faulty parts can and
should be done with the appliance isolated from
the supply. Remove the plug or fuse supplying the
appliance. If the fuse is removed, steps should be
taken to prevent another person inadvertently
replacing it.)
(b) Is it absolutely necessary for someone to be
working on or near an appliance that is live at
dangerous voltages or current levels?
(c) Have suitable precautions been taken to avoid
danger and, where necessary, prevent injury?
(d) Is the person doing the work competent for that
type of work, or, if not, adequately supervised?
What precautions should I take?
Where possible, the work should be done with the
equipment dead (this is a requirement of the Electricity
at Work Regulations 19893). Otherwise, adequate
precautions, which should be identified in your risk
assessment, must be taken to ensure safety.
The following precautions are recommended as part of a
safe system of working for electrical testing of this
equipment.
Test areas
In all circumstances, it is necessary to create a safe
working environment for testing. A test area in which the
work is to be done should be defined. This should be
relatively straightforward in a workshop situation, but
may be more difficult when working in a customer’s
home.
Safety in electrical testing: Servicing
and repair of domestic appliances
HSE information sheet
Engineering Information Sheet No 35
In the customer’s home
When working in a customer’s home, the person
carrying out the testing should carry out a site risk
assessment to determine the steps necessary to create
a safe working environment.
(a) If you do not think it is safe to work in the home,
don’t. Remove the equipment to the workshop
where you can work safely;
(b) Consider erecting a temporary barrier to prevent
unauthorised people approaching the danger area;
(c) Allow plenty of space to work in. If you do get a
shock you may be less able to break contact
quickly, if at all, or are more likely to hit something
if you are working in a cramped area. Remove (or
move away from) any objects that may pose a
hazard. For example, if an appliance is situated in
a corner, consider pulling it out and working behind
it;
(d) Make sure everyone in the home is aware of the
dangers arising from the testing work, and that they
follow any precautions that are necessary. Ask for
children and pets to be kept from the area;
(e) Never leave an appliance unattended when it is in
a dangerous condition (eg with live conductors
exposed).
In the workshop
When testing is being done in a workshop, the following
precautions should be considered:
(a) Access to the test area should be limited as far as
is practicable to the competent persons carrying
out the testing. Suitable barriers may be provided
to help prevent unauthorised entry. Competent
persons must have adequate knowledge of the
electrical dangers associated with the appliances
and the precautions necessary to reduce the risk of
electric shock. Training must be provided as
necessary;
(b) Other people who may enter the test area from
time to time should be instructed about the hazards
that may be present and in particular be told not to
touch anything on the work bench. Their access
should be limited to what is strictly necessary;
(c) Adjacent test positions should be separated using
barriers to prevent a tester from reaching into
another test area;
(d) Soak test areas should, where possible, be
separate from the test benches and when
equipment is on soak test, its covers should be in
place.
Access to live parts
Where diagnostic testing needs to be carried out on live
appliances, the risk is most effectively controlled by
preventing access to the live parts. This can be achieved
in a number of ways:
(a) Prevent accidental contact with dangerous
conductors by the use of temporary insulation. This
could be commercially available transparent and
perforated material to allow moving parts to be
observed and for access to test probes.
Additionally, individual sleeves can be placed over
conductors. This may be difficult where the
conductor areas are small (connection size). In
these cases, ensure that a safe system of work,
incorporating the other relevant precautions listed
below, is being followed;
(b) The power supply should include a Residual
Current Device (RCD), with a rated tripping current
of, at most, 30mA. This may not be available on all
customers’ circuits, so a portable RCD should be
available;
(c) When printed circuit boards are being tested and
are taken out of the normal working position,
secure them in purpose-built jigs to provide
adequate support and to prevent them from falling;
(d) When working on microwave ovens, ensure that
the high-voltage internal source is not energised
while the oven cover is removed. Functional testing
to show whether or not the magnetron is operating
should be done with covers fitted.
Test equipment
Where possible, test equipment should be of a
proprietary design. In this case the manufacturer should
have taken account of its safety performance during use.
Where applicable, test equipment should be
manufactured to BS EN 61010,4 BS EN 615575 or
BS EN 61243-3.6
Purpose-built test equipment must be designed and
constructed to the same standards of safety as
proprietary equipment. Where equipment is mains
powered, it must be safe to use as a piece of electrical
equipment in its own right. In addition, the arrangements
for connecting it to the equipment under test must be
safe.
See also advice given in Safety in electrical testing at
work: General guidance 2 concerning the use of test
equipment.
Power supply earthing
When working on Class I (earthed enclosure) equipment
it is important that the earthing of the power supply to
the equipment is adequate and efficient. In customers’
premises this is likely to be unknown so it is important to
carry out a test to demonstrate the efficacy of the
earthing. The safe way to do this is to measure the earth
loop impedance of the power supply using an instrument
designed for that purpose. Make sure that you know
how to use the testing device and how to interpret the
results obtained. If the test indicates an inadequate
earth, the customer must be informed that the work
cannot continue until it has been rectified.
Remember that simple 'Go/No go' plug-in testers will in
general only provide a polarity check and an indication
that an earth may be present, but not its effectiveness.
What are the legal requirements?
The Electricity at Work Regulations 19893 are the
principal legislation relating to electrical testing activities
and regulation 14 is particularly relevant to live testing
activities. In addition, employers are required under
regulation 3 of the Management of Health and Safety at
Work Regulations 19997 to assess the risks to the health
and safety of their employees while they are at work, in
order to identify and implement the necessary
precautions to ensure safety.
References
1 Safety in electrical testing: Servicing and repair of
audio, TV and computer equipment Engineering
Information Sheet EIS35 HSE Books 2002
2 Safety in electrical testing at work: General
guidance Leaflet INDG354 HSE Books 2002 (single
copy free or priced packs of 5 ISBN 0 7176 2296 7)
3 Memorandum of guidance on the Electricity at
Work Regulations 1989. Guidance on Regulations
HSR25 HSE Books 1989 ISBN 0 7176 1602 9
4 BS EN 61010: 1993 Safety requirements for
electrical equipment for measurement, control and
laboratory use (full document is in 11 parts)
5 BS EN 61557: 1997 Electrical safety in low voltage
distribution systems up to 1000 V ac and 1500 V dc.
Equipment for testing, measuring or monitoring
protective measures
6 BS EN 61243-3: 1997 Live working. Voltage
detectors. Two-pole low voltage type
7 Management of health and safety at work.
Management of Health and Safety at Work Regulations
1999. Approved Code of Practice and guidance L21
(Second edition) HSE Books 2000 ISBN 0 7176 2488 9
Where can I get more information?
Electrical test equipment for use by electricians GS38
HSE Books 1995 ISBN 0 7176 0845 X
Electricity at work: Safe working practices HSG85
HSE Books 1993 ISBN 0 7176 0442 X
BS EN 50191: 2001 Erection and operation of electrical
test equipment
DASA Quality criteria (Section 2 ‘Competence’ and 3.1
‘Electrical safety tests’) Domestic Appliance Service
Association (DASA), 69 The Maltings, Stanstead
Abbotts, Herts SG12 8HG Tel: 01920 870173 (available
free on request)
While every effort has been made to ensure the
accuracy of the references listed in this publication, their
future availability cannot be guaranteed.
Further information
HSE priced and free publications are available by mail
order from HSE Books, PO Box 1999, Sudbury, Suffolk
CO10 2WA Tel: 01787 881165 Fax: 01787 313995
Website: www.hsebooks.co.uk (HSE priced publications
are also available from bookshops.)
For information about health and safety ring HSE's
InfoLine Tel: 08701 545500 Fax: 02920 859260 e-mail:
hseinformationservices@natbrit.com or write to HSE
Information Services, Caerphilly Business Park,
Caerphilly CF83 3GG. You can also visit HSE’s website:
www.hse.gov.uk
British Standards are available from BSI Customer
Services, 389 Chiswick High Road, London W4 4AL
Tel: 020 8996 9001 Fax: 020 8996 7001
Website: www.bsi-global.com
This publication may be freely reproduced, except for
advertising, endorsement or commercial purposes. The
information is current at 03/02. Please acknowledge the
source as HSE.
This leaflet contains notes on good practice which are
not compulsory but which you may find helpful in
considering what you need to do.
Printed and published by the Health and Safety Executive 03/02 EIS35 C200

general safety for electricity

2011-07-12T06:00:00.001-07:00

Electrical
safety
and you
1
INTRODUCTION
Electricity can kill. Each year about 1000 accidents at work involving electric shock
or burns are reported to the Health and Safety Executive (HSE). Around 30 of
these are fatal. Most of these fatalities arise from contact with overhead or
underground power cables.
Even non-fatal shocks can cause severe and permanent injury. Shocks from faulty
equipment may lead to falls from ladders, scaffolds or other work platforms.
Those using electricity may not be the only ones at risk: poor electrical
installations and faulty electrical appliances can lead to fires which may also cause
death or injury to others. Most of these accidents can be avoided by careful
planning and straightforward precautions.
This leaflet outlines basic measures to help you control the risks from your use of
electricity at work. More detailed guidance for particular industries or subjects is
listed on pages 6 - 8. If in doubt about safety matters or your legal responsibilities,
contact your local inspector of health and safety. The telephone number of your
local HSE office will be in the phone book under Health and Safety Executive. For
premises inspected by local authorities the contact point is likely to be the
environmental health department at your local council.
WHAT ARE THE HAZARDS?
The main hazards are:
■ contact with live parts causing shock and burns (normal mains voltage,
230 volts AC, can kill);
■ faults which could cause fires;
■ fire or explosion where electricity could be the source of ignition in a
potentially flammable or explosive atmosphere, eg in a spray paint booth.
ASSESSING THE RISK
Hazard means anything which can cause harm.
Risk is the chance, great or small, that someone will actually be harmed by the
hazard.
2
The first stage in controlling risk is to carry out a risk assessment in order to
identify what needs to be done. (This is a legal requirement for all risks at work.)
When carrying out a risk assessment:
■ identify the hazards;
■ decide who might be harmed, and how;
■ evaluate the risks arising from the hazards and decide whether existing
precautions are adequate or more should be taken;
■ if you have five or more employees, record any significant findings;
■ review your assessment from time to time and revise it if necessary.
The risk of injury from electricity is strongly linked to where and how it is used.
The risks are greatest in harsh conditions, for example:
■ in wet surroundings - unsuitable equipment can easily become live and
can make its surroundings live;
■ out of doors - equipment may not only become wet but may be at
greater risk of damage;
■ in cramped spaces with a lot of earthed metalwork, such as inside a tank
or bin - if an electrical fault developed it could be very difficult to avoid
a shock.
Some items of equipment can also involve greater risk than others. Extension
leads are particularly liable to damage - to their plugs and sockets, to their
electrical connections, and to the cable itself. Other flexible leads, particularly
those connected to equipment which is moved a great deal, can suffer from
similar problems.
More information on carrying out risk assessments is available in other HSE
publications listed on page 6 of this leaflet.
REDUCING THE RISK
Once you have completed the risk assessment, you can use your findings to
reduce unacceptable risks from the electrical equipment in your place of work.
There are many things you can do to achieve this; here are some.
Ensure that the electrical installation is safe
■ install new electrical systems to a suitable standard, eg BS 7671 Requirements
for electrical installations, and then maintain them in a safe condition;
■ existing installations should also be properly maintained;
■ provide enough socket-outlets - overloading socket-outlets by using
adaptors can cause fires.
Provide safe and suitable equipment
■ choose equipment that is suitable for its working environment;
■ electrical risks can sometimes be eliminated by using air, hydraulic or handpowered
tools. These are especially useful in harsh conditions;
■ ensure that equipment is safe when supplied and then maintain it in a safe
condition;
■ provide an accessible and clearly identified switch near each fixed machine
to cut off power in an emergency;
■ for portable equipment, use socket-outlets which are close by so that
equipment can be easily disconnected in an emergency;
■ the ends of flexible cables should always have the outer sheath of the cable
firmly clamped to stop the wires (particularly the earth) pulling out of the
terminals;
■ replace damaged sections of cable completely;
■ use proper connectors or cable couplers to join lengths of cable. Do not
use strip connector blocks covered in insulating tape;
■ some types of equipment are double insulated. These are often marked with
a ‘double-square’ symbol . The supply leads have only two wires - live
(brown) and neutral (blue). Make sure they are properly connected if the
plug is not a moulded-on type;
■ protect lightbulbs and other equipment which could easily be damaged in
use. There is a risk of electric shock if they are broken;
■ electrical equipment used in flammable/explosive atmospheres should be
designed to stop it from causing ignition. You may need specialist advice.
Reduce the voltage
One of the best ways of reducing the risk of injury when using electrical equipment
is to limit the supply voltage to the lowest needed to get the job done, such as:
3
4
■ temporary lighting can be run at lower voltages, eg 12, 25, 50 or 110 volts;
■ where electrically powered tools are used, battery operated are safest;
■ portable tools are readily available which are designed to be run from a
110 volts centre-tapped-to-earth supply.
Provide a safety device
If equipment operating at 230 volts or higher is used, an RCD (residual current
device) can provide additional safety. An RCD is a device which detects some, but
not all, faults in the electrical system and rapidly switches off the supply. The best
place for an RCD is built into the main switchboard or the socket-outlet, as this
means that the supply cables are permanently protected. If this is not possible a
plug incorporating an RCD, or a plug-in RCD adaptor, can also provide additional
safety.
RCDs for protecting people have a rated tripping current (sensitivity) of not more
than 30 milliamps (mA). Remember:
■ an RCD is a valuable safety device, never bypass it;
■ if the RCD trips, it is a sign there is a fault. Check the system before using it
again;
■ if the RCD trips frequently and no fault can be found in the system, consult
the manufacturer of the RCD;
■ the RCD has a test button to check that its mechanism is free and
functioning. Use this regularly.
Carry out preventative maintenance
All electrical equipment and installations should be maintained to prevent danger.
It is strongly recommended that this includes an appropriate system of visual
inspection and, where necessary, testing. By concentrating on a simple, inexpensive
system of looking for visible signs of damage or faults, most of the electrical risks
can be controlled. This will need to be backed up by testing as necessary.
It is recommended that fixed installations are inspected and tested periodically by
a competent person.
The frequency of inspections and any necessary testing will depend on the type of
equipment, how often it is used, and the environment in which it is used. Records
5
of the results of inspection and testing can be useful in assessing the effectiveness
of the system. More detailed guidance is available in the booklets listed on pages
6 - 8.
Equipment users can help by reporting any damage or defects they find.
Work safely
Make sure that people who are working with electricity are competent to do the
job. Even simple tasks such as wiring a plug can lead to danger - ensure that people
know what they are doing before they start.
Check that:
■ suspect or faulty equipment is taken out of use, labelled ‘DO NOT USE’ and
kept secure until examined by a competent person;
■ where possible, tools and power socket-outlets are switched off before
plugging in or unplugging;
■ equipment is switched off and/or unplugged before cleaning or making
adjustments.
More complicated tasks, such as equipment repairs or alterations to an electrical
installation, should only be tackled by people with a knowledge of the risks and the
precautions needed.
You must not allow work on or near exposed live parts of equipment unless it is
absolutely unavoidable and suitable precautions have been taken to prevent injury,
both to the workers and to anyone else who may be in the area.
Underground power cables
Always assume cables will be present when digging in the street, pavement or near
buildings. Use up-to-date service plans, cable avoidance tools and safe digging
practice to avoid danger. Service plans should be available from regional electricity
companies, local authorities, highways authorities, etc.
Overhead power lines
When working near overhead lines, it may be possible to have them switched off if
the owners are given enough notice. If this cannot be done, consult the owners
6
about the safe working distance from the cables. Remember that electricity can
flash over from overhead lines even though plant and equipment do not touch
them. Over half of the fatal electrical accidents each year are caused by contact
with overhead lines. More detailed guidance on avoidance of danger from
overhead electric lines is available from HSE.
Electrified railways and tramways
If working near electrified railways or tramways, consult the line or track
operating company. Remember that some railways and tramways use electrified
rails rather than overhead cables.
HSE GUIDANCE ON ELECTRICAL SAFETY
The following publications contain advice on the safe use of electricity for
particular industries or in high risk circumstances.
Risk assessment and general health and safety
5 steps to risk assessment INDG163(rev1) HSE Books 1998 (single copies free
or priced packs of 10 ISBN 0 7176 1565 0)
Essentials of health and safety at work HSE Books 1994 ISBN 0 7176 0716 X
Maintenance of portable electrical equipment
Maintaining portable and transportable electrical equipment HSG107
HSE Books 1994 ISBN 0 7176 0715 1
Maintaining portable electrical equipment in offices and other low-risk environments
INDG236 HSE Books 1996 (single copies free or priced packs of 10
ISBN 0 7176 1272 4)
Maintaining portable electrical equipment in hotels and tourist accommodation
INDG237 HSE Books 1996 (single copies free or priced packs of 10
ISBN 0 7176 1273 2)
General electrical guidance
Avoiding danger from underground services HSG47 (Second edition)
HSE Books 2000 ISBN 0 7176 1774 0
Avoidance of danger from overhead electrical lines GS6(rev) HSE Books 1997
ISBN 0 7176 1348 8
Electrical safety on construction sites HSG141 HSE Books 1995
ISBN 0 7176 1000 4
Electricity at work - safe working practices HSG85 HSE Books 1993
ISBN 0 7176 0442 X
Electrical test equipment for use by electricians GS38(rev) HSE Books 1995
ISBN 0 7176 0845 X
Electrical safety at places of entertainment GS50 HSE Books 1997
ISBN 0 7176 1387 9
Electrical hazards from steam/water pressure cleaners etc PM29(rev)
HSE Books 1995 ISBN 0 7176 0813 1
Selection and use of electric handlamps PM38 HSE Books 1992
ISBN 0 11 886360 6
Memorandum of guidance on the Electricity at Work Regulations 1989 HSR25
HSE Books 1989 ISBN 0 7176 1602 9
GUIDANCE ON ELECTRICAL SAFETY FROM OTHER
ORGANISATIONS
Note: The inspection and testing intervals for electrical equipment given in these
publications are recommendations and are not legal requirements.
BS 7671: 2001 Requirements for electrical installations. IEE Wiring Regulations
16th edition. The IEE Wiring Regulations have the status of a British Standard.
They are supported by a separate series of Guidance Notes enlarging on
particular requirements of parts of the Regulations.
Code of practice for in-service inspection and testing of electrical equipment
Both titles are available from:
Institution of Electrical Engineers
PO Box 96
Stevenage, Herts SG1 2SD
7
8
FURTHER INFORMATION
This leaflet is available in priced packs of 15 from HSE Books,
ISBN 0 7176 1207 4. Single free copies are also available from HSE Books.
HSE priced and free publications are available by mail order from HSE Books,
PO Box 1999, Sudbury, Suffolk CO10 2WA Tel: 01787 881165
Fax: 01787 313995 Website: www.hsebooks.co.uk (HSE priced publications are
also available from bookshops.)
For information about health and safety ring HSE's InfoLine Tel: 08701 545500
Fax: 02920 859260 e-mail: hseinformationservices@natbrit.com or write to
HSE Information Services, Caerphilly Business Park, Caerphilly CF83 3GG.
You can also visit HSE’s website: www.hse.gov.uk
This publication may be freely reproduced, except for advertising, endorsement or
commercial purposes. The information it contains is current at 3/98.
Please acknowledge the source as HSE.
Printed and published by the Health and Safety Executive
INDG231 Reprinted 11/03 C500
This leaflet contains notes on good practice which are not compulsory but which
you may find helpful in considering what you need to do.
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2391 introduction

2011-07-12T05:58:00.001-07:00

Introduction
The notes for this course have been drawn up to aid electricians in their understanding of
the requirements for testing as detailed in Part 6 of IEE Wiring Regulations, 17th Edition
(BS7671 : 2008).
References for the tests described have been taken from Guidance Notes No 3 entitled
'Inspection and Testing' published by the Institute of Electrical engineers.
Whilst every effort has been made to ensure that the information given in these notes is
correct and complete all parties making use of these notes should rely on their own skill
and judgment when using them.
These notes are not intended to replace the need for the 17th edition of the IEE Wiring
Regulations which should be referred to as the definitive source for questions arising in
relation to electrical installations.

Index
Chapter 1 Standards & Regulations
1.1 Standards page 4
1.2 Plan of the IEE Wiring Regulations page 5
1.3 Safety page 6
1.4 Competent Persons page 7
Chapter 2 Earthing Systems
2.1 Reasons for Earthing
2.2 Earth Fault Path
2.3 Earthing Arrangements
Chapter 3 Inspection
3.1 General Requirements
3.2 Initial Inspection
3.3 Periodic Inspection
3.4 Frequency of Inspection & testing
Chapter 4 Testing
4.1 Sequence for Testing
4.2 Continuity of Protective Conductors
4.3 Continuity of Ring Final Circuit Conductors
4.4 Insulation Resistance
4.5 Site Applied Insulation
Protection by Separation of Circuits
Protection by Barriers or Enclosures
Insulation of Non-conducting Locations
4.6 Polarity
4.7 Earth Electrode Resistance
4.8 Earth Fault Loop Impedance
External Earth Fault Loop Impedance
Prospective Short Circuit Current
4.9 Residual Current Devices
4.10 Functional Tests
4.11 Periodic Tests

Chapter 5 Documentation
5.1 Electrical Installation Certificate
5.2 Alterations and Additions
5.3 Periodic Inspection Report
5.4 Minor Works
Chapter 6 Instrumentation requirements

1.1– Standards
It is necessary to understand the reasons for producing regulations which specify
standardized methods associated with the installation, inspection and testing of electrical
installations.
The Electricity Supply Regulations, 1988 and Electricity at Work Regulations, 1989, are
statutory regulations which have to be complied with in terms of safety and workmanship.
An electrical installation which complies with the 17 th Edition of the IEE Wiring
Regulations is viewed by the HSE as likely to achieve conformity with the relevant parts of
the Electricity at Work Regulations, 1989.
Certain types of premises, such as petrol stations, cinemas, night clubs etc.,are subject to
licensing. With this type of premises, statutory regulations which may add to, or differ from
the requirements of the IEE Wiring Regulations, apply. In this case the licensing
requirements would take precedence over the IEE Wiring Regulations.
ln certain areas of electrical work, where the requirements of the IEE Wiring Regulations
are not specific enough, reference will need to be made to the relevant British Standard
covering that subject.
ln addition to the above, due to the UK's membership of the EEC, it is seen as essential
that electrical installation practice be standardized throughout the Community.
CENELEC, the specifying and standards authority for all electrical technical matters for
Europe, have produced Harmonization Documents. In the preface to the IEE Wiring
Regulations these documents and their direct comparison with the relevant parts of the IEE
Wiring Regulations are listed.
Whilst differences of opinion do exist between the IEE Wiring Regulations Committee and
CENELEC on certain subjects, in theory a knowledge of the IEE Wiring Regulations will
enable an electrician to work in any Country within the EEC and to produce work which is
acceptable to the inspection authorities within that county.
By the acceptance of the IEE Wiring Regulations as a British Standard in October of 1992,
the regulations took on the required international standing. This now means that
electricians from other parts of the EEC wishing to carry out electrical work within the UK
are also bound by the IEE Wiring Regulations.

1.2 Plan of the IEE Wiring regulations
Whilst standardization is desirable, it does pose problems. The 17th Edition of the IEE
Wiring Regulations have been laid out according to the pattern agreed for CENELEC
documents which does not always make it easy for one to locate all the regulations
pertaining to a specific topic as these may not be located within the same section.
The major advantage of the current edition of the IEE Wiring Regulations over previous
versions is that it does contain a much improved index.
The Regulation numbers are set out in the arrangement as defined by the internationally
agreed standard for electrical installations, for example.
413.03.03
4 th part (Protection for safety)
Chapter 1 (Protection against electric shock)
Section 3 of chapter (Protective measure: Electrical separation)
Regulation 3 (Requirements for fault protection)
Finally part 3 of the regulation. (Live parts of a separated circuit shall not be connected to
any other circuit or to Earth or to a protective conductor)
The 17th Edition I.E.E. Wiring Regulations or BS7671 can be divided into 7 different
sections.
Part 1 Scope,object & fundamental Requirements for Safety
Part 2 Definitions
Part 3 Assessment of General Characteristics
Part 4 Protection for Safety
Part 5 Selection & Erection Of Equipment
Part 6 Inspection &Testing (Part 7 in the 16th edition)
Part 7 Special Installations or Locations (Part 6 in the 16th edition)
Appendices tables and information required to design a system
Part 1. Scope,Object & Fundamental Requirements For Safety
Chapter 11 - Scope.
Chapter 12 - Objects & Effects.
Chapter 13- Fundamental Principles.

Part 2
Definitions
Part 3. Assessment of General Characteristics
Chapter 31 - Purpose, supplies & Structure
Chapter 32 - Classification of External Influences
Chapter 33 - Compatibility
Chapter 34 - Maintainability
Chapter 35 - Safety Services
Chapter 36 - Continuity of service.
Part 4. Protection For Safety
Chapter 41 - Protection Against Electric Shock
Chapter 42 - Protection Against Thermal Effects
Chapter 43 - Protection Against Over current
Chapter 44 - Protection Against Voltage disturbances and electromagnetic disturbances.
Part 5. Selection & Erection of Equipment
Chapter 51 - Common Rules
Chapter 52 - Selection & Erection of Wiring Systems
Chapter 53 - Protection, isolation, switching, control and monitoring.
Chapter 54 - Earthing Arrangements & Protective Conductors
Chapter 55 - Other Equipment
Chapter 56 - Supplies for Safety Services
Part 6. Inspection & Testing (was part 7 in 16th edition)
Chapter 61 - Initial Verification
Chapter 62 - Periodic Inspection & Testing
Chapter 63 - Certification & Reporting
Part 7. Special Installations Or Locations (was part 6 in 16th edition)
Section 700 - General
Section 701 - Locations Containing a Bath or a Shower
Section 702 - Swimming Pools and other basins
Section 703 - Rooms and cabins containing Sauna heaters
Section 704 - Construction and demolition Site Installations
Section 705 - Agricultural & Horticultural Premises
Section 706 - Conductive locations with Restrictive movements
Section 708 -Electrical Installations in Caravan, camping parks and similar locations.

Part 7. Special Installations Or Locations(cont)
Section 709 - Marinas and similar locations
Section 710 – Medical locations Reserved for Future Use
Section 711 - Exhibition installation's, shows, stands, displays.
Section 712 - Solar Photovoltaic (PV) power supply systems (solar power)
Section 717 - Mobile or transportable unit.
Section 721 - Electrical installations in Caravans and Motor Caravans.
Section 740 - Temporary Installation's for structures, amusements and devices used at
fairgrounds, amusements and circuses
Section 753 - Floor and Ceiling heating systems
Appendices
1 British Standards to which reference is made in the Regulations.
2 Statutory Regulations & associated memorandums.
3 Time/current characteristics of overcurrent protective devices & RCDs
4 Current carrying capacity and volt drop for cables & flexible cords.
5 Classification of external influences.
6 Model forms for certification and reporting.
7. Harmonized cable colours
8 Current carrying capacity and volt drop for busbar trunking and powertrack systems.
9 Definitions multiple source, DC and other systems.
10 Protection of conductors in parallel against overcurrent.
11 Effect of harmonic currents on balances in 3 phase systems
12 Voltage drop in customers installations
13 Methods of measuring the installation resistance or impedance of floors and walls to
earth or to the protective conductor system.
14 Measurement of fault loop impedance with consideration on the increase in resistance
to the conductors with the increase in temperature.
15 Ring and radial final circuit arrangements, Regulation 433.1
The IEE also publish a set of and guidance notes to be used in conjunction with the
regulations.
1 Selection and erection of equipment
2 Isolation and switching
3 Inspection and Testing
4 Protection against fire
5 Protection against electric shock
6 Protection against overcurrent
7 Special locations
The On Site guide published by the IEE provides a short form guide for installations up to
100 amps per phase. It also includes many useful tables and checklists.

1.3 Safety
Electrical testing involves some degree of hazard both to oneself and to other people. As
the regulations primary concern is with the safety of persons, livestock and property, safe
working practices are a must. Safety procedures as detailed in the HSE Guidance Note
GS38 Electrical test equipment for use by electricians' should be observed at all times.
As regards fundamental safety, special note should be taken of Chapter 13 of the IEE
Wiring Regulations BS7671 (page 14) and this should then be compared with the
requirements of the EAWR,1989. It will be seen that these two documents exist in total
harmony as to their aims in regard to the safe use of electricity.
1.4 Competent, Person's Responsible for Inspection and Testing
As we progress through the course it will be appreciated that the person carrying out the
inspection and test of the installation will be responsible for deciding whether or not an
installation complies with the regulations in their entirety.
These course notes will be concentrating on Part 6 of the Regulations. These notes can
not be viewed as a replacement for the Regulations nor can they replace the need for a
sound working knowledge of the Regulations. It will seen that reference must be made to
the other Parts and Appendices within the Regulations other than Part 6.
Therefore the person carrying out the installation (IEE reg 134.1.1 page 19) and the
inspection and testing of any electrical installation work must competent (IEE reg 610.5
page 156). Competency encompasses skills, experience and technical knowledge. The
inspector needs to have experience and knowledge of the type of installation he will be
working on so as to ensure that danger to persons, livestock or property does not occur.

2.1 Reason for Earthing?
The ground under our feet, in fact the whole world can be considered as a conductor which
is at zero potential.
A shock hazard occurs when a person makes contact with two points which are at different
potentials. As people are in contact with the ground which is at zero potential there is a
danger that touching any other surface that may be at a different potential to this will result
in a shock being encountered.
By connecting all those parts, which may become charged to a different potential, to the
general mass of earth, we will do away with the possibilities of shock hazard. By the use of
earthing we also aim to provide a low resistance path for fault currents to flow through,
enabling a high current to flow and the protective device to open.
Electricity always takes the easiest path whether it is through the human body or through
the intended earth conductor. From this we can see the importance of keeping the
impedance of earth paths as low as possible.
The standard method of tying the electrical supply system to earth is by making a direct
connection between the two. This usually entails connecting the neutral or start point of the
three phage supply transformer to earth.
From this we can be fairly certain that the neutral of the system is at, or near zero volts and
that the line conductor will differ from this by 230 volts. We can also see that neutral and
earth will be at the same potential.
By connecting all metal work not intended to carry current to earth by means of protective
conductor, a path is provided for fault currents to flow. This is illustrated and discussed in
the next section.

2.2 Earth loop path
The earth fault loop of a circuit (Zs) includes the following,
Starting from the fault point:
The fault point
The circuit protective conductor
The main earthing terminal
The main earthing conductor
The earth return path
The path through the earth and neutral point of the transformer
The transformer winding
The line conductor from the transformer to the point of fault.
See diagram on page 11

Of what use to us is the measuring of the earth fault loop or Zs of a circuit?

If we know the value of it we can use Ohms Law to calculate the fault current that will flow
if a fault occurs.
The formula we can apply is: voltage = current
resistance
From this we can see that Fault Current and Earth Fault Loop Impedance are directly
linked, the lower the earth fault loop the higher the fault current and vice versa.
Therefore, the lower the earth fault loop, the higher the fault current, the quicker the
protective device will operate to cut off the current. If we limit the maximum value of the
earth fault loop we can be confident that the fault current will be of a higher magnitude to
operate the protective device before dangerous shock can occur.(IEE reg 411.3.2 page 46)
The values of Earth loop impedance are compared to tables in the regulations to determine
the required disconnection times are achieved. (IEE reg Table 41.2 page 48)
For example if a BS 1361 fuse is to be used as our protective device, for a disconnection
time of less than 0.4 seconds in a circuit with a Uo of 230 volts and rated at 20 amps the
maximum Zs value is 1.70 Ω.
More values for disconnection times can be found in Appendix 3 which have graphs and
tables for most of the common types of protective devices.
Using a BS 1361, 20 amp fuse, for a disconnection time of 0.1 sec what current would be
required to flow in order to satisfy the 0.1 second disconnection time?
IEE reg fig 3.1 (page 244) shows a graph and a table. The graph plot start at 0.1 sec and
for a 20 amp fuse it intersects the current lines at just under the 200 amp mark.
This can be confirmed by examining the table in the far right hand corner which confirms
that a current of 180 amps must flow to enable the fuse to disconnect within 0.1 seconds.

2.3 Earthing Arrangements
Electrical systems are classified according to their earthing arrangements. The following
letter designations are used:
The first letter indicates the Supply earthing arrangements.
T One or more points of the supply are directly connected to earth
I supply system not earthed, or one point earthed through a fault
limiting impedance. (Not used in this Country)
The second letter indicates the Installation earthing arrangements
T exposed conductive parts connected directly to earth
N exposed conductive parts connected directly to the earthed point of
the source of the electrical supply.
The third letter indicates the Earthed Supply Conductor arrangement
S separate neutral and protective conductors
C neutral and protective conductors combined in a single conductor.
The types of system detailed in the Wiring Regulations are: IEE part 2 definitions (page
32)
TN-S TN-C-S TN-C TT IT

TN-S System
With this system the neutral and CPC are separate throughout the system. This type of
system applies to underground cables where the metal sheath of the supply cable is
connected to the consumers earth terminal and therefore provides a continuous earth path
back to the star point of the supply transformer.
TT Systems
With this system the Supply Company do not provide an earth terminal. The supply is
usually via overhead lines. The consumer has to provide an electrode to connect the
protective conductors of the installation to earth. Effective earth connection is sometimes
difficult to obtain so therefore a residual current device will need to be installed.

TN-C-S Systems
With this system the Supply Company uses a combined protective and neutral (PEN)
conductor, at this stage the supply is a TN-C system. The consumer installation will consist
of separate neutral and protective conductors (TN-S). This combination is known as TN-CS.
The majority of new installations are of this type and are referred to as a PME supply.
TN-C
With this system the neutral and protective conductors are combined in a single conductor
throughout the installation. This type of arrangement can only be used with permission
from the appropriate authority.
IT Systems
This type of system has either no earth connection or is connected via a high impedance.
This type of system is not allowable in the UK but is included in the Regulations for
European harmonization.

3.1- General Requirement
IEE reg 610.1 (page 156) Every installation shall, during erection and/or on completion
before being put into service be inspected and tested to verify, so far as reasonably
practicable, that the requirements of the Regulations have been met.
The reasons for an inspection and test of an electrical installation is to verify that the
installation complies with the Regulations with regard to its Design and Construction. To
help the person carrying out the inspection to for fill these requirements the Regulations
call for the following Information to be made available:
The results of the assessment of general characteristics required by sections 311,312 and
313.
This would include:
1.The Maximum demand for the installation
2.The Number and type of live conductors ie, single phase two wire ac. Three phase four
wire ac.
3.Type of earthing arrangement ice. TN-C-S TN-S TN-S (See Chapter 2.3)
4.Nominal Voltage
5.Nature of current and frequency
6. Prospective Short Circuit Current at the origin of the installation
7. External Earth Fault Loop impedance Ze (see Chapter 4.8)
8. Type and rating of overcurrent device at the origin of the installation.
The Regulations also call for the information to a be made available as (IEE reg 514.9
page 93).This may be in the form of a chart. This would provide all the necessary
information as to circuit type, number of points and their positions, cable sizes, protective
device types and their ratings etc.
Without the above information the person responsible for the inspection will not be able to
carry out his job.

3.2 Initial Inspection
IEE reg 611.1 (page 156) Inspection shall precede testing and shall normally be done with
that part of the installation disconnected from the supply.
Guidance Note 3 suggests some 180 items to which special attention should be paid
during the Inspection process. From this it can be seen that a complete and concise list is
impossible to compile.
In the majority of cases deviations from the Regulations which one will come across while
carrying out the inspection will be down to the experience of the inspector rather than the
ticking of a checklist. From our discussions so far you will see that experience as well as a
sound working knowledge of the Regulations is a must.
It should always be in mind that the Regulations state (IEE reg 134.1.1 page 19)
Good workmanship by a competent person or persons under their supervision and proper
materials shall be used.
(IEE reg 612.2 page 156) calls for the inspector to confirm that equipment has been
selected in accordance with section 511 of the Wiring Regulations, and the equipment's
compliance with the relevant British or equivalent Standard.
It also calls for confirmation that, this equipment has been correctly selected and installed,
is suitable for the environment, and has no visible damage that may impair safety.
It can be seen from this that the Inspector has immense responsibility placed upon him as
to the safety of the installation.
Visual Inspection is essential to assess the safety of an installation before testing takes
place.

(IEE reg 611.3 page 156) The inspection shall include at least the checking of the following
items, where relevant to the installation and, where necessary, during erection.
It should be noted from the above that the inspection of some of the items can only be
carried out during installation as they will be hidden from view upon completion.
The minimum inspection should include where relevant the following items:
1) Connection of conductors
2) Identification of conductors
3) Routing of cables in safe zones or protection against mechanical damage
4) Selection of conductors for current-carrying capacity and voltage drop, in accordance
with the design
5) Connection of single-pole devices for protection or switching in line conductors only
6) Correct connection of accessories and equipment
7) Presence of fire barriers and protection against thermal ejects
8) Methods of protection against electric shock
9) Prevention of mutual detrimental influences
10) Presence of appropriate devices for isolation and switching correctly located.
11) Presence of undervoltage protective devices.
12) Labelling of protective devices switches and terminals.
13) Selection of equipment and protective measures appropriate to external influences.
14) Adequacy of access to switchgear and equipment.
15) Presence of danger notices and other warning signs.
16) Presence of diagrams, instructions and similar information.
17) Erection methods.
(a) Method for Basic and Fault protection, i.e
SELV
Limitation of discharge energy
(b) Method for Basic protection (including measurement of distances where
appropriate), i.e:
Protection by insulation of live parts
Protection by a barrier or an enclosures
Protection by obstruction
Protection by placing our of reach
Protection by PELV

c) Method for Fault protection.
Earthed equipotential bonding and automatic disconnection of supply Presence of earthing
conductors
Presence of protective conductors
Presence of main equipotential bonding conductors
Presence of supplementary equipotential bonding conductors
Presence of earthing arrangements for combined protective and functional purposes
Use of class 2 equipment or equivalent insulation
Non-conducting location (including measurement of distances, where appropriate)
Absence of protective conductors
Earth-free local equipotential bonding
Presence of earth-free equipotential bonding conductors
Electrical separation

3.3- Periodic inspection (IEE chapter 62 page 162)
Periodic inspection is somewhat different to the initial inspection procedure.
The above Regulation refers to 'Careful Scrutiny' backed up by testing.
Visual Inspection is the VITAL initial operation and testing is in support of this Visual
Inspection.
In many cases diagrams and circuit charts will not be available so some exploratory work
will be required. The Visual Inspection shall be concerned with the Verification that the
safety of persons, livestock and property has not or will not be endangered.
A thorough Visual Inspection shall be made of all electrical equipment which is not
concealed. It will include many of the items listed under initial inspection.
It is a requirement of the Regulations that the person ordering the work be informed of the
need for Periodic Inspection and Testing. Installations which are subject to licensing have
mandatory intervals between tests which must be followed. Guidance Note 3 gives
guidance as to recommended intervals.

Table 2.1.5 Recommended initial frequencies of inspection of electrical installations
Type of installation Routine check
sub-clause 2.1.4
Maximum period between
inspections and testing as
necessary
References
(see notes below)
General installations
Domestic
Commercial
Educational establishments
Hospitals
Industrial
Residential accommodation
Offices
Shops
Laboratories
1 year
4 months
1 year
1 year
1 year/ Change of
occupancy
1 year
1 year
1 year
Change of tenancy 10 years
Change of tenancy 5 years
5 years
5 years
5 years
5 years
5 years
5 years
5 years
1,2
1,2
1,2
1
1,2
1,2
1,2
Building open to the public.
Cinemas
Church installations
Leisure complexes
Places of public
entertainment
Restaurants and Hotels
Theatres
Public Houses
Village halls/ Community
Centres
4 months
1 year
4 months
4 months
1 year
4 months
1 year
1 year
1 year
5 year (quinquennially)
1 year
1 year
5 years
1 year
5 years
5 years
2,6,7
2
1,2,6
1,2,6
1,2,6
2,6,7
1,2,6
1,2
External Installations
Agricultural and Horticultural
Caravans
Caravan Parks
Highway power supplies
Marinas
Fish farms
1 year
1 year
6 months
as convenient
4 months
4 months
3 years
3 years
1 year
6 years
1 year
1 year
1,2
1,2,6
1,2
1,2
Special Installations
Emergency Lighting
Fire Alarms
Launderettes
Petrol Filling stations
Construction site installations
Daily/ Monthly
Daily/ weekly/
Monthly
1 year
1 year
3 months
3 years
1 year
1 year
1 year
3 months
2,3,4
2,4,5
1,2,6
1,2,6
1,2
Reference Key
1. Particular attention must be taken to comply with SI 1988 No 1057. The Electricity Supply Regulations 1998 (as amended).
2. SI 1989 No 635. The Electricity at Work Regulations 1989 ( Regulation 4 and Memorandum
3. See BS 5266:Part 1: 1988 Code of Practice for the emergency lighting of premises other than cinemas and certain other specified
premises used for entertainment.
4. Other intervals are recommended for testing operation of batteries and generators
5. See BS5839: Part 1:1988 Code of practice for system design and installation and servicing (Fire detection and alarm systems for
buildings)
6. Local Authority Conditions of Licence
7. SI 19995 No 1129 (Clause 27) The Cinematograph (Safety) regulations.

4,1 - Sequence of Tests
Testing of electrical installations can be divided into two distinct parts:
Tests to be carried out before the supply is connected, or with the supply disconnected.
Within this section the sequence for testing is:
(a) 4.2 Continuity of protective conductors, main and supplementary
bonding
(b) 4.3 Continuity of ring final circuit conductors
(c) 4.4 Insulation resistance
(d) 4.5 Site Applied Insulation
Protection by separation of Circuits
Protection by Barriers or Enclosures Provided During Ere
Insulation of Non-conducting Floors and Walls
(e) polarity
(f) Earth electrode resistance
Once the electrical supply has been connected recheck polarity using a suitable mains
voltmeter then carry out the following tests:
(a) 4.8 Earth fault loop impedance
External Earth Fault Loop Impedance
Prospective Short Circuit Current
(b) 4.9 Residual current operated devices
(c) Functional test of switchgear etc

Isolation
Before continuing with the tests consideration must be taken with the subject of isolation of
the circuit.
When isolating it should be confirmed that after isolation the expected circuits are not live
by the use of a suitable test meter set to the suitable voltage setting.
The isolation method should be locked of by either removal of fuses, which are then
secured. Or the application of a locking device.
A notice should be placed at the isolation point to confirm the circuit is isolated and warning
not to re energize the circuit.
These are important steps in the test procedures, they should be included in any procedure
both in working practice and practical or written examination.
4.2 Continuity of Protective Conductors
(IEE reg 612.2.1 page 158)
The above regulation requires that every protective conductor including bonding
conductors shall be tested to verify that they are electrically sound and correctly
connected,
Note: Guidance Note 3 states that
For cables having conductors of a cross- sectional areas not exceeding 35mm their
inductance can be ignored. Above that figure the inductance becomes significant and an
A/C. Instrument should be used for the measurement.
We are unaware of any Company who at the present time manufactures or sells such an
instrument.
For the purpose of the following tests a continuity tester able to read to a resolution of
0.01ohms is required. The full specification is detailed in the chapter dealing with
Instrumentation Requirements.

Test method 1 - Linking line and CP conductors at the distribution board.
Connect a temporary link between the line and the CPC conductors. Using a low
resistance ohmmeter test between the line and earth terminals at each outlet in the circuit.
The measurement obtained at the furthest point of the circuit should be recorded on the
results schedule. This reading is the value R1+R2.
Points to note
Multi Meter set to the low Ω range
a = Temporary link between line and CPC at the consumer unit.
All fuses should be removed or MCB'S switched off Main switch switched off.
* Ensure Removal of temporary link when testing is complete.

Test Method 2 Long lead Method
Connect one terminal of the ohmmeter to the earth terminal at the distribution board via a
lead long enough to reach the farthest extremity of the circuit under test. The other terminal
is then used to make contact with each outlet on the circuit.
Once the resistance of the test leads is subtracted from the readings the figures can be
recorded.
Points to note
Multi Meter set to the low Ω range
Note All fuses out or MCB'S switched off Main switch turned off

From the foregoing descriptions it can be seen that in the majority of cases Method 1 will
be the preferred method. For the testing of bonding conductors Method 2 is the only
applicable method.
Where the protective conductor has been sized according to the alternative method to
IEE reg 411.3.2 62 page 46 of the Regulations a separate measurement of the protective
conductor is required using Method 2.
lt should be noted that the aforesaid methods of test can only be applied to an 'all insulated'
installation'
Installation's incorporating steel conduit or trucking, m.i.c.c. and swa cables will
introduce parallel earth paths which will effect the test readings.
Precautions will need to be taken to identify and eliminate these effects while testing. It can
be seen from this that this stage of testing may have to take place during the installation
process rather than being left till the end.
Guidance Note 3 contains details of the procedures to be followed when steel conduit, etc.
is relied upon as the protective conductor further test can be summarized as follows:
A standard continuity test as detailed in Tests 1 & 2 above. This should be followed by a
visual inspection along the length of the protective conductor path to identify any obvious
points where problems may arise.
The majority of electricians these days will not choose to use steel conduit, etc as the
protective conductor for a circuit, so the above problems should not arise.

4.3 Continuity of Ring Final Circuit Conductors
(IEE reg 612.2.2 page 158) A test shall be made to verify the continuity of each conductor
including the protective conductor, of every ring dual circuit.
As a rink circuit relies on both sets of three conductors to be connected for the circuit to
meet the design criteria as regards current carry capacity and short circuit protection, and
due to the fact that faults occurring may not be immediately apparent, ie. the circuit will still
function with one 'Live' conductor disconnected, it can be seen that testing is of utmost
importance.
Tests need to be carried out to Confirm that line, neutral as well as CPC form uninterrupted
rings.
Correctly connected ring circuit showing equal current sharing on each leg of the ring.

Possible Dangerous Ring Circuit Faults
Here a brake has occurred in on leg of the ring circuit, this results in the cable on the other
leg of the ring becoming overloaded, especially towards the consumer unit side of the leg,
the load could be 27A .

A bridge in the circuit hides the fact the ring is not complete, this fault would not be picked
up in the test for the continuity of CPC, as tested earlier pages 24 and 25.

Test 1 To Confirm the ring is complete
Each individual leg of the ring needs to be identified. The line conductor of one leg of the
ring is conceded to the neutral conductor of the other at the distribution board. The
resistance is measured between the remaining line and neutral conductors. This test
confirms that both the line and neutral conductors form rings.
Points to note
Multi Meter set to the low Ω range

This above test is repeated using the line conductor and the circuit protective
conductor.
Test 2 to confirm the absence of bridges

lt is possible that Test 1 will indicate that the ring is complete, because of a bridge in the
ring as per page 29. This shortening of the ring could cover up the fact that the ring may be
broken at another point, resulting in an overloading of the cables at that point.
Test 2 confirms that the above situation does not exist.
With the conductors connected as in Test 1, connect the remaining line and neutral
conductor together. The resistance been line and neutral at each outlet is then measured.
This reading will remain substantially the same at each outlet that is incorporated into the
ring provided that no multiple loops exist. This test will also indicate any outlets which may
be connected as a spur to the ring.
The values should be within 0.05 Ω of each other.
Points to note
Multi Meter set to the low Ω range

The above test is repeated using the line conductor and the circuit protective conductor.
The highest reading taken is considered as the measured value of R1+R2.
The values should be within 0.05 Ω of each other.

Results
Where the protective conductor is in the form of a ring, the above two tests will need to be
repeated, substituting the protective conductor for the neutral conductor in each test.
The reading obtained in Test 2 at each outlet between the line conductor and protective
conductor will be equal to the value of R1 + R2 for that circuit and should be recorded. This
result will also be equal to one quarter of the value obtained in Test 1.
When testing between line conductor and protective conductor.
R1+R2 = result of Test 2 = result of test 1
4
While it should be easy to identify each leg where multi core cables are used, this may not
be the case where single core cables are used. An error in identification and connection of
the legs of the ring will be immediately apparent while conducting Test 2.
An error in this respect will show up as progressively increasing readings towards the
midpoint of the ring and then a decrease away from the midpoint. If this encountered then
the error in connection will need to be rectified and both Tests 1 & 2 repeated.

Insulation tests
(IEE reg 612.3 page 158)
These tests are to confirm that the insulation of conductors and equipment is satisfactory
and that short circuits do not exist.
Testing is carried call with an insulations tester that generates the required voltage as
specified in Table 61 of the regulations at a current of 1mA.
In the case of electrical installation up to and including 500V the test voltage required will
also be 500V.
Whereas in the past the Regulations called for various pieces of electrical equipment to be
disconnected from the mains and for lamps etc to be removed this is now recognized as
not always practical.
The Regulations now state that 'where appropriate line and neutral conductors may be
connected together and a test to earth carried out. Simple installations which do not
contain distribution circuits may be tested as a whole rather than as individual circuits.
Although Table 61 calls for an insulation value of not less than 1 megohms for an
installation of up to 500V if the result is below 2 megohms each circuit will need to be
tested separately The-result for individual circuits must exceed 1 megohms.
Example of IEE reg table 61 page 158
Minimum values of insulation resistance and meter test voltage settings
Circuit nominal voltage
(V)
Test voltage D.C
(V)
Minimum insulation
resistance
(MΩ)
SELV and PELV 250 ≥ 0.5
Up to and including 500v
with the exception of the
above systems
500 ≥ 1.0
Above 500v 1000 ≥ 1.0

Insulation test for a complete installation
Points to note
Meter set to a test voltage of 500 volts DC (IEE reg table 61 page 158), for testing a 230
volt circuit
Range set to MΩ
The main switch is isolated
All fuses are in and MCB's switched on.
A temporary link is placed between the line a neutral conductors
All fuses should be left in place or MCB'S switched on Main switch switched off.
• Ensure Removal of temporary link when testing is complete.

•
Three Phase
Testing of three phase circuits involves making a series of tests. The conductors will be
grouped into two groups and an insulation test carried out between the two groups.
Group A Group B
Test 1 Phase 1 Phase 2
Phase 3
Neutral
Test 2 Phase 2 Phase 3 Neutral
Test 3 Phase 3 Neutral
Test 4 Phase 1 Earth
Phase 2
Phase 3
Neutral
Where it is not possible to group conductors as above, they may be tested singularly.

4.5 Other Tests
Guidance Note 3 includes several tests which we do not intend to cover in any great detail
within these course notes. For further details reference should be made to the Guidance
notes.
The relevant tests are as follows:
Site Applied Insulation
This test is only applicable where insulation is applied during installation. It involves the use
of a high voltage tester capable of apply a voltage of 3750 V
Protection be Separation of Circuits
This relates to the testing of SELV and FELV transformers to confirm separation of primary
and secondary parts of the circuit.
Protection by Barriers or Enclosures Provided During Erection
This test does not apply to factory built equipment, but only to those provided on site during
the course of assembly or erection. It is concerned with checking that the enclosure meets
the relevant ip rating.
Protection by a non conducting Location
This deals with insulation of non-conducting floors and walls. It includes details of the
required high voltage testing.

4.6 Polarity Testing
(IEE reg 612.6 page 159) A test of polarity shall be made and it shall be verified that :-
Every fuse and single-pole control and protective device is connected in the line conductor
only,
Center-contact bayonet and Edison screw landholders to BS EN 60238 in circuits having
an earthed neutral conductor have the outer or screwed contacts connected to the neutral
conductor;
Wiring has been correctly connected to socket-outlets and similar accessories.
If a switch or fuse is connected in the Neutral conductor of a circuit rather than in the line
conductor, mains potential voltages will continue to be present throughout the circuit when
the switch is opened or the fuse pulled.
This would give rise to the scenario of a circuit appearing to be 'dead' but in actual fact
posing very real danger.
Use an Ohmmeter or the continuity range of an Insulation and Continuity tester for this
sequence of tests.

Method 1 - Linking the Line and CP conductors at the Distribution Board
The method used here is the same as the test described as method 1 for checking the
continuity of protective inductors. This involves connecting a temporary link between the
line conductor and the protective conductor. And then checking at each outlet, including
switch positions, for a low resistance reading between line and Earth.
Ensure that the circuit is isolated before carrying out this test
Remove the link after the test.

Method 2 - Using a Long Lead
Method 2 involves using a long lead. One end of the long lead is connected to the line
conductor at the distribution board and the other end is connected to one terminal of the
ohmmeters The other lead of the Ohmmeter is then used to check each line connection
throughout the circuit for continuity.
If the tests for ring circuits have been carried out as described, correct connection will
already have been verified and no further testing is required
Ensure that the circuit is isolated before carrying out this test

4.7 Earth Electrode resistance
IEE reg 612.9 page 160 Where protective measures are used which require a knowledge
of the earth electrode resistance, this shall be measured.
Testing to check Compliance with IEE reg: 415.2.2 Page 59
Method 1 Using a Dedicated Earth resistance Tester (Figure 4.7)
The earth electrode under test needs to be disconnected from the earthing system of the
installation. As this electrode is likely to be the primary means of earthing for the
installation, this will necessitate the complete isolation of the installation for safety reasons.
Two temporary earth spikes are driven into the ground for testing purposes. The distance
between these earth spikes is important. If the earth spikes are placed too close together
their resistance areas will overlap and false readings will be obtained.
The first, or 'current' spike is driven into the ground at a distance away, from the electrode
under test , equivalent to 10 times the length of the electrode under test.
ie. for an earth electrode 2 meters long the current spike should be placed 20 meters away
from the electrode under test.
The second, or 'potential' spike, is driven into the ground midway between the electrode
under test and the 'current' spike. The earth electrode resistance tester is connected and a
reading is taken. The 'potential' spike is then moved 10% closer to the earth electrode
under test and another reading taken. The 'potential' spike is then moved 10% closer to the
'current' spike and a final reading taken.
The average of the three readings is taken. If there is a difference greater than 5%
between any of the above three readings and the calculated average, then the test
distance between the earth electrode under test and the 'current' will need to be increased
and the above testing procedure repeated.
Upon Completion, Ensure Bonding is reconnected before switching on the
instillation.
Figure 4.7

Test method 2 Using a Loop Impedance meter
Testing For compliance with IEE reg: 411.4.5 (page 48)
This method is intended as an alternative to method 1 for TT installations where the earth
electrode is used in conjunction with a residual current device to provide fault protection.
As with method 1 the main bonding needs to be disconnected from the equipotential
bonding. This is to eliminate the possibility of erroneous readings due to parallel earth
paths and to ensure that the full test current passes through the earth electrode under test.
A loop impedance tester is connected between the line conductor at the source of the
installation and the earth electrode under test. The impedance reading taken is treated as
the electrode resistance.
Upon Completion, Ensure equipotential Bonding is reconnected before switching
on the installation.

Results
What results should we be looking for?
What we are trying to accomplish with our use of earth electrodes is to make sure that
when a fault occurs the voltage between earthed metalwork and earth will not exceed 50
volts.
Where an RCD with a tripping current of 30mA is used, this means that if we apply Ohms
Law to the problem, we would come up with a theoretical value of 1.666ohms
50 V
0.03 A = 1,666 Ohms
BS 7430 Code of Practice for Earthing suggests that earth electrodes with values
exceeded 220 ohms are prone to be unstable.
Maximum values for earth electrodes will more likely be dictated by other regulations such
as HS(G)41 detailing petrol station installations, which calls for a value not exceeding 21
ohms.
Obviously the lower the resistance of the earth electrode the better.

4.8 Earth Fault Loop Impedance
IEE reg: 612.9 (page 160) Where protective measures are used which require a
knowledge of earth fault loop impedance, the relevant
impedance's shall be measured, or determined by an
alternative method.
Testing for compliance with IEE reg: 411.4.5 (page 48)
Earlier on in the notes we discussed the meaning of Earth Fault Loop impedance and we
saw the reasons for limiting its upper value.
The earth fault loop impedance (Zs) should be determined at the furthest point of each
circuit. This includes socket outlets, lighting points, sub-main cables and other circuits
supplying fixed current using equipment.
Method
Measuring of the earth fault loop impedance (Zs) for circuits incorporating socket outlets
involves no more than plugging in the loop tester and taking a reading. The result obtained
includes the earth fault loop external to the installation (Ze).
For other circuits such as lighting circuits or circuits feeding fixed equipment not connected
via a plug and socket, use will have to be made of a purpose designed set of leads and
probes.
A loop tester which does not trip RCD will need to be used or the value calculated.
With the loop tester, the neutral connection is there only to power the test instrument.
Where a neutral is not available, such as in a 3 phase motor circuit the neutral lead will
need to be conceded to earth along with the earth lead of the tester.

Results
Once we have obtained an earth fault loop impedance reading to what does one compare
it? IEE reg: 411.3.2 (page 46) including table Table 41.1 give the required disconnection
times for TN and TT systems.
IEE Tables 41.2, 41.3, 41.4 and 41.5 (pages 48,49 and 50) of the Wiring regulations give
maximum earth fault loop impedance's for various types and ratings of MCB'S and fuses. It
should be noted that these values are intended as design values only. When a person
responsible for the design of a circuit calculates the maximum earth fault loop or Zs for a
circuit the formula is as follows:
Zs = Ze + (R1+R2)
Where:
Zs = Earth Fault Loop Impedance of the System
Ze = Earth Fault Loop Impedance External to the Installation
RI = Resistance of the line conductor from the origin of the circuit to the furthest point of
utilization.
R2 = Resistance of the protective conductor from the origin of the circuit to the furthest
point of utilization
Under fault conditions the temperature of the conductors will rise until the fault current
reaches a point where the overcurrent protective device operates. To take a account of
this rise in temperature the designer applies a factor to the R1+R2 figure before comparing
his figures with the values shown in IEE Tables 41.2, 41.3, 41.4 and 41.5 (pages 48,49
and 50) . The values for this factor can be found in the 'On Site Guide' published by the
IEE.
Obviously our testing takes place at a temperature far less than the temperature the cable
reaches under fault conditions. To take this into account we would have to apply the same
multiplier as well as to correct the values of R1 and R2 for differing temperature.
Alternatively we could compare our readings with the maximum values detailed in the 'On
Site Guide' , published by the IEE, as the figures contained within this publication have
been adjusted to take the above into account.
Another acceptable method is to divide the reading obtained by our loop tester by a factor
of 0.75. This applies to protective devices listed in the regulations. For protective devices
not listed the factor is 0.66.
i.e.: For a loop tester reading of 1 ohm the adjusted value will be 1 =1.33 ohms
0.75
This value can then be compared directly with tables IEE Tables 41.2, 41.3, 41.4 and 41.5
(pages 48,49 and 50)

Measurement of the External Earth Fault Loop Ze
The Ze or, External Earth Fault Loop impedance, is measured using a phase earth loop
impedance tester at the source of the installation supply. The outgoing supply needs to be
isolated along with the means of earthing, which involves isolating the main bonding
conductor from all other earthing conductors. The reason for isolating the main earth is to
remove the possibility of erroneous readings due to parallel earth paths.
Do Not Forget To Reconnect Bonding

Measurement of Prospective Short Circuit Current
Prospective Short Circuit Current (PSCC) is the current likely to flow in a circuit under fault
conditions. It is the largest current that is likely to flow in a circuit. Protective devices such
as fuses,MCB must be able to break this fault current safely and should be selected in
accordance with the PSCC.
PSCC = Uo
Zt + Z1 + Z 2
where.
Zt = Impedance of transformer winding
Z1 = Impedance of line conductor
Z2 = Impedance of Neutral conductor
U0 = Voltage
By Using a loop tester to measure the line - Neutral loop we can calculate the PSCC.

4.9 Residual Current operates Devices
IEE reg 612.10 (pages 160) Where RCD's are required for additional protection, the
effectiveness of automatic disconnection of supply by RCD's shall be verified using
suitable test equipment according to BS EN 61557-6 (see regulation 612.1) to confirm that
the relevant requirements of Chapter 41 are met.
In order to test the effectiveness of an RCD it is necessary to carry out a series of tests to
confirm that the RCD operates within correct time and current parameters. This sequence
of tests is in addition to using the integral test button incorporated in the RCD. IEE reg
612.13.1 (page 161)
The test is made on the load side of the RCD, between the line conductor and the CPC of
the circuit. The test current is obtained from the live and neutral of the circuit under test.
Any loads connected should be disconnected.
The sequence of tests is:
1)To apply a current equal to 50% of the rated tripping current of the RCD for a period of 2
seconds. The RCD should not trip.
2)Application of a current equal to 100% of the rated tripping current of the RCD. The RCD
should operate within 200mS.
3)Where the RCD is used to provide supplementary protection for basic protection, a test
current of 150 mA is applied for a maximum period of 50 mS. The RCD should operate
within 40 mS.
4)The integral test button incorporated in the RCD is now operated. This checks the
operation of the mechanical parts of the RCD. It does not check the continuity of the
protective conductors or the rest of the earthing system.
The above sequence and results apply to non delayed RCD'S complying with BS 4293. For
time delayed RCD'S the results for test 2 should be within the following range:
50% of rated time delay plus 200mS, and
100% of rated time delay plus 200mS
i.e For an RCD with a delay of 200mS it should trip within a time range of:
( 100 + 200 ) mS = 300mS and
( 200 + 200 ) mS = 400mS

Testing of 3 Phase RCD'S
With certain 3 phase circuits protected by RCD'S a neutral may not be available. As the
RCD tester obtains its test current from the line and neutral of the circuit under test this
poses a problem. We can overcome this by connecting the neutral lead of the tester to
earth. However, it should be noted that the test current will be increased and may trip the
RCD on the 50% test. The RCD should not necessarily be failed in this instance.
Safety
Care must be exercised while carrying out the testing of RCD'S as potentially dangerous
voltages may appear on exposed and extraneous conductive parts when the earth fault
loop impedance approaches the maximum acceptable limit.

4.10 Functional Test Of Switchgear
IEE reg 612.13.2 (page 161)
Assemblies such as switchgear and control gear assemblies, drives controls and
interlocks, shall be subjected to a functional test to show that they are properly
mounted adjusted and installed in accordance with the relevant requirements of these
Regulations.
As a final test the above should be carried out. This would include the switching off and on
of MCB'S etc, to make sure that their mechanical operation is satisfactory.

4.11 Periodic Testing
Periodic testing of an installation should be carried out in the following order:
(a) Continuity of protective conductors and earthed equipotential bonding.
(b) Polarity.
(c) Earth fault loop impedance.
(d) Insulation resistance.
(e) Operation of devices for isolation and switching.
(f) Operation of residual current devices.
Where appropriate, the following tests should also be made:
(g) Continuity of ring circuit conductors.
(h) Earth electrode resistance.
(i) Manual operation of overcurrent protective devices other than fuses.
(j) Electrical separation of circuits.
(k) Protection by non-conducting floors and walls
How much testing needs to be done?
Guidance Note 3 suggests that a random selection of points is tested. This should be equal
to 10% of the installation. If faults were discovered within this batch the batch should be
expanded to 25% and then on to 100% if further faults are discovered.
All socket outlets should be checked for correct polarity.
When checking the continuity of bonding or equipotential bonding conductors the
installation should be isolated from the mains. On no account should bonding conductors
be disconnected with the mains on.

5.1 Certification and Reporting
Chapter 63
Once the initial verification ( this includes both inspection and testing) has been completed
the above regulations call for the issuing of an Electrical Installation Certificate, together
with a schedules of test results. This Certificate should be given to the person ordering the
work. The above mentioned Certificate would be incomplete and void if a schedule of test
results was not included.
Who is responsible for signing the certificate? The Certificate includes space for three
signatures, the person responsible for the Design, the person responsible for the
construction and the person carrying out the Inspection and Test of the installation.
It should be emphasized that the signature for the Inspection and Test section is the
person who actually carries out the Inspection and Test and not someone else who may be
in authority. In some cases all three sections will be signed by the same person. This is
perfectly acceptable.
The Electrical Installation Certificate should not be signed until any defects, which the
person responsible for inspection and test may have identified, have been corrected.
Alterations and Additions
An Electrical Installation Certificate as above or a Minor Electrical Installation Works
certificate , stating the extent of the works covered, shall be issued once the Inspector is
satisfied that the works comply with the Regulations. Any defects found in related parts of
the installation, not effecting the safety of the alteration or addition, should be reported in
writing to the person ordering the work.
If existing defects effect the new work then these defects would have to be corrected
before an Electrical Installation Certificate could be issued and before the new work could
be put into service. An example of this is where bonding or equipotential bonding is
inadequate or omitted as this would seriously effect the safety of the whole installation
including the new work.
The Electrical Installation Certificate should not be used for Periodic Inspections.

Periodic Inspection report
The Periodic Inspection Report form is only to be used for the inspection of an existing
installation. It shall include both inspection and test results.
Again the Extent and Limitations as to the report shall be stated. Recommendations as to
defects and their remedied shall be made.
The report includes a numbering system for this purpose, as follows:
1 Requires Urgent Attention
2 Requires Improvements
3 Requires Further Investigation
4 Does Not Comply With BS 7671:2008 (as amended)
(this does not necessarily imply that the electrical installation is unsafe)
Again, with the Periodic Inspection and Test the main consideration is safety.

Minor Works certificate
Several associations and trade bodies allow the issuing of a 'Minor Works Certificate'. A
minor works is defined as 'work which does not include the provision of a new circuit'
Testing is still essential and the following tests should be carried out to confirm safety.
The Tests are as follows:
1) Circuit impedance R1+R2
2) Insulation Resistance line/Earth
Neutral/Earth
3) Earth Fault loop Impedance
4) Polarity
5) RCD Operation
Included on the form is space to allow the Inspector to comment on the existing installation.

6.1- instrumentation requirements
Continuity Tester
Accuracy +/- 2%
Resolution 0.01 ohms
No Load Voltage 4 - 24v ac or dc
Test Current 200 mA
Insulation Resistance
Accuracy +/- 2%
Test Current 1 mA at the minimum allowable resistance value
i.e 250k for 250v range
500k for 500v range
1M for 1000v range
Other requirements i.e. Must have the capability to discharge capacitance which has
become charged during the test.
Earth Electrode Resistance Tester
Accuracy +/- 2%
Other requirements Facility to check potential and current spikes are within the
testers limits.
Loop Impedance Tester
Accuracy +/-2%
Test Current 20-25A for up to two or four cycles
RCD Testers
Accuracy of test currents + /- 10%
Accuracy of times +/-5%
Time resolution 1mS
Other requirements Able to perform tests for Reg. 713-12
Suitable for RCD ratings of 6,10,30,100 & 500mA
Must apply 150mA test current for no longer than 50mS

International Protection provided by
Enclosures
I.P Ratings
To BS EN 605299

Number Degree of
protection against
ingress of solid
foreign objects
Number Degree of
protection against
ingress of water
0 Not protected 0 Not protected
1 Protected against
access to hazard
parts by back of hand
Protection against
foreign objects of
50mm diameter and
greater.
1 Protection against
vertically falling water
drops
2 Protected against
access to hazard
parts by a finger
Protection against
foreign objects of
12.5mm diameter
and greater.
2 Protection against
vertically falling water
drops when
enclosure tilted at 15º
3 Protection against
tools wires and
others 2.5mm and
greater
3 Protection against
water spraying up to
an angle of 60º on
either vertical side.
4 Protection against
tools wires and
others 1mm and
greater
Protection against
foreign objects of
1mm diameter and
greater.
4 Protection against
water splashing from
any direction.
5 Protection against
tools wires and
others 1mm and
greater
Dust protection
5 Protection against
water jets from any
angle.

Number
Degree of
protection against
ingress of solid
foreign objects
Number
Degree of
protection against
ingress of water
Dust may enter but
not interfere with the
operation of the
device
6 As above 6 Protection against
powerful water jets
from any angle.
No code 7 Protection against
ingress of water
when enclosure is
immersed in water in
standard conditions

Degrees of Protection provided by Enclosures
This was better known as Ingress Protection
IP Code Of Protection. -
This C of P is given in BS EN 60390-2, this document is the standard document, which is
used to form the basic requirements of electrical equipment Standards.
The construction for IP ratings of a specific type of equipment are given in a British
Standard document.
Also in the document are the relevant construction requirements for various plugs and
socket outlets, including ( BS 4343 -- now BS EN 60309-2 ), that is why there is no nation
of this IP classification in BS 7671 .
The degree of protection provided by this enclosure is indicated by two numerals and
followed by an optional letter and /or optional two supplementary letters as follows
IP Coded letters International Protection
First characteristic numeral, (from 0 - 6, or could be letter X, not defined )
Second characteristic numeral, (from 0 - 8 or could be letter X.)
Additional letter (optional ) ; A, B, C, D
Supplementary letter (optional ); H, M, S, W.
the reference could be IP 23CH
Where there is a non specific reference, the numbers can be replaced by the letter X ie. IP
XX , if both the numbers are omitted.
The additional letter / (s) can be omitted without replacement.
Where more than one letter is used then the alphabetical sequence shall apply.

Degrees of Protection provided by enclosures
The ADDITIONAL Letter
Supplementary Letter
In the relevant product standard classification, supplementary information may be indicated
by a supplementary letter following the second characteristic numeral or the additional
letter.
The following letters are currently in use, but extra letters will probably be used as the
standards of various products change.
Product Marking
The requirements for marking a product are specified in the relevant product standard.
For example, IP23CS
The IK code of impact PROTECTION

This IK code of classification was introduced to provide protection for electrical equipment
against mechanical impart.
The code classifies the degree of protection.
Continental countries have their own classification, the IK is now The UK classification,
where there was no previous classification for mechanical impact.
The obvious reason for the introduction of this classification in this country, is that we as a
nation are increasingly selling our products in Europe.
They need to understand our reference with respect to their own.
The standard only describe the general requirements and designations of the system the
application of the system to a specfic enclosure type will be covered by the BS which is
applicable to the enclosure
The IK coding used is marked separately on The equipment from the IP rating.
Coded letters IK Characteristic group 00 to 10
each group represents an impact energy value as shown in the table below

Drip Proof and Splash Proof
Certain electrical equipment has been graded against water ingress by a pictorial
representations which is now superseded by the IP rating, nevertheless these should be
able to be identified and recognized and understood.
The comparisons between the differing references are not exact, but the installer, designer
and the tester of such equipment must be able to recognize the seals used, so that the
equipment being used is suitable for the location of use.

Choice of Protective Devices
The selection of protective devices depends upon :
l . prospective fault current
2. circuit load characteristics
3. cable current – carrying characteristics
4. disconnection time limit.
Show circuit capacities of the protective devices Device type
Device Short-circuit Device Spec Short Circuit Capacity kA
Semi-enclosed fuse to BS 3036 S1A 1
S2A 2
S4A 4
Cartridge fuse to BS 1361 16.5
33.0
General purpose fuse to BS 88 50 @ 400v
16.5 @ 230v
80 @ 400v
Circuit breakers to BS 3871 M1 1
M1.5 1.5
M3 3.0
M4.5 4.5
M6 6.0
M9 9.0
Icn Ics
Circuit Breakers to BS EN 60898 1.5 (1.5)
3.0 (3.0)
6.0 (6.0)
10 (7.5)
15 (7.5)
25 (10)
Icn = rated ultimate S / C capacity.; Icn > Ipsc , except where it is used as back-up
protection ref To manufactures information
lcs = This is the max level of fault current operation after which further service is assumed
without loss of performance Protective devices must cater for both: -protection
against overload/ short circuit protection

2392 exam preparation

2011-07-12T05:57:00.001-07:00

This Section is highlight the areas covered by the 2392-10 syllabus. Student are expected
to have knowledge of all that is in the syllabus.
For this qualification, candidates will be required to successfully complete both of the
following assessments:
One closed-book multiple-choice online test covering the underpinning knowledge of
outcomes 1-3 (2392-101)
Practical assessment unit (2392-102)
It will be graded pass or fail.
Duration: 100 minutes
No of questions: 50
Outcome number Unit title Number of
items
Approximate
percentage %
1 Preparation for inspection and testing 8 16
2 Inspection 6 12
3 Testing 32 72
Total 50 100
Fundamental Initial Verification of Electrical Installations
There are three areas to this unit:
Preparation for initial inspection and testing
Inspection
Testing
It is recommended that 30-35 hours should be allocated for this unit.
Preparation for initial inspection and testing
The candidate will be able to, given the information required:
Carry out the Initial Verification (inspection, testing and certification) of an installation to
BS 7671
Complete an Electrical Installation Certificate (as given in BS 7671 or Guidance Note 3),
for the installation, including the Schedule of Test Results
Carry out an inspection of installation components and complete the Schedule of
Inspections.
The candidate will be able to demonstrate knowledge of:
Requirements for Initial Verification
Information required to correctly conduct the initial inspection and testing of an
installation
Statutory and non-statutory requirements and relevant guidance materials which apply to
the activity of inspecting and testing of electrical installations
Need to comply with statutory and non-statutory requirements, guidance material for
particular locations and environments in which electrical installations are installed
Essential and optional information to be contained on the Electrical Installation
Certificate and Minor Electrical Installation Works Certificate and how the information is
recorded.

Inspection
Carry out the Initial Verification (inspection, testing and certification) of an installation to
BS 7671
Complete an Electrical Installation Certificate (as given in BS 7671 or Guidance Note 3),
for the installation in item 3, including the Schedule of Test Results
Carry out an inspection of installation components and complete the Schedule of
Inspections.
State the human senses that may need to be employed during the Initial Verification of
an installation
Refer to and select the items to be checked during the inspection process for given
systems and locations
State the requirements of the Electricity at Work Regulations for safe inspection and
testing in terms of those carrying out the work and those using the installation and the
building during the inspection and testing.
Testing
Select the correct instruments or functions and appropriate scales to carry out tests
Check and prove instruments and leads for safety and function
Carry out the Initial Verification (inspection, testing and certification) of an installation to
BS 7671
Complete an Electrical Installation Certificate (as given in BS 7671 or Guidance Note 3),
for the installation in item 3, including the Schedule of Test Results
Carry out an inspection of installation components and complete the Schedule of
Inspections.
State the need for instruments to be regularly checked and the need for compliance with
the requirements of BS 7671 (current edition) and HSE Guidance Note GS 38
List the correct instruments, functions and appropriate scale(s) to carry out each test and
explain the reasons for each choice
State the recommended sequence of tests covered by this unit and the reasons for that
sequence

Protective Conductors
State the requirements which need to be considered for protective conductors in terms of
a earthing conductors
b main protective bonding conductors
c supplementary equipotential bonding conductors
d circuit protective conductors
Describe the need for, and methods of, verifying the continuity of protective conductors
and the interpretation of results
State the relationship between conductor length, cross sectional area (csa) and resistance
State the effect of temperature on conductor resistance.
Ring Final Circuits
State the effect on conductor resistance when cables are connected in parallel
Describe the need for, and the method of verifying the continuity of, ring final circuit
conductors and the interpretation of results
State the relationship between conductor length and conductor resistance.
Insulation Resistance
Explain, by example, the effect on insulation resistance of
a cables connected in parallel
b variation in cable length
State the difference between measurements taken for insulation resistance and conductor
resistance, and the order of magnitude that would be expected in each case
State the preconditions required for the performance of insulation resistance testing in
terms of
a client consultation
b safety procedures and notices
State the precautions to be taken before testing insulation resistance in terms of
a isolation of circuits and equipment
b voltage sensitive equipment
c electronic components

Describe methods of testing insulation resistance
State the required test voltages and minimum values of insulation resistance for circuits
operating at various voltages
SELV
Describe the test to verify separation between SELV circuits and other circuits.
Special Installations and locations
State the requirements for locations containing baths or showers in terms of
a circuits
b equipment
c zones.
IP Code
State the appropriate degrees of protection required for given locations and environments
afforded within the IP classification BS EN 60529.
Polarity
State the reasons for tests to confirm correct polarity
Describe the methods of testing used to identify correct polarity
State the reasons for confirming correct polarity following initial energising of installations.
Earth Electrodes
State the instruments used for testing earth electrodes as
a Earth electrode resistance tester
b Earth fault loop impedance tester
Describe the method testing earth electrode resistance using an earth fault loop
impedance tester.
Earth Fault Loop Impedance
Describe the earth fault loop impedance paths for the following systems
a TN-S
b TN-C-S

c TT
Describe methods of determining earth fault loop impedance in terms of
a the tests used for measuring actual earth fault loop impedance
b methods of calculation of earth fault loop impedance from given data and measurement
of conductor impedance
Given maximum tabulated values of earth fault loop impedance, verify that measured
values are acceptable, taking into account conductor operating and ambient temperatures
Residual Current Devices (RCD)
Describe methods of testing the correct operation of an RCD, independent of in-built test
facilities
State the applications for various RCD ratings
State the requirements for RCD in series.
Prospective Fault Current
Describe prospective fault current in terms of
a prospective short-circuit current
b prospective earth fault current
State methods of determining prospective fault current
Describe the methods of measuring prospective fault current
Explain the importance of confirming that protective devices are appropriate for the
prospective fault current.
Verification of voltage drop
State the methods of evaluating voltage drop
Determine compliance with voltage drop from given criteria.

Practical Assessment Practical Assessment Requirements 2392-102 Inspection,
Testing and Certification – practical
This practical assessment element must be completed, in addition to 2392-101, for
candidates to gain a certificate.
The practical assessment consists of one assessment.
The test procedure should be completed within the time indicated. The candidate should
be continuously monitored during the test procedures.
Where candidates supply their own test instruments and/or tools, the assessor is
responsible for verifying the suitability of these for the tasks to be undertaken.
Test procedure
The candidate should be given
An Electrical Installation Certificate, the Schedule of Test Results and Schedule of
Inspections for the assessment
A selection of hand tools, where required, to carry out testing of the installation
A range of test instruments including those required to complete the tests.
The information contained within the candidate section of the 2392-102 Assessment
Guide.
Candidate identification and other relevant information should be completed on the
appropriate result sheet prior to the commencement of each test.
The candidate will be expected to record all relevant information and results for all circuits
on the appropriate documents.
The tests and performance criteria for assessment
The tests that must be completed and the detailed performance criteria the candidate must
meet in order to pass the test are provided in the Assessment Guide for Centres. A copy of
each set of performance criteria must be completed for each candidate.
Consideration should be given to the Electricity at Work Regulations throughout the
assessment process, and it should be made clear to the candidate that failure to observe
appropriate safe working practices will result in the assessment being stopped.

2391 exam preparation

2011-07-12T05:56:00.001-07:00

2391 concern about past exams

2011-07-12T05:52:00.000-07:00

These notes have been compiled while the 16th edition was in place. They are from the
exam bodies notes and pick up on the areas in which the students sitting the exam are
making the most errors. The introduction of the 17th edition has changed some of the
terms used. Please take these into consideration before the examination.
Use of correct terminology
Correct terminology must be used as detailed in BS 7671 and Guidance Note Three
(GN3), must be used when answering questions . Students out-dated terms, and incorrect
terminology. For example:
the use of “live” instead of phase (phase in the 17th edition is referred to as line conductor)
“Completion Certificate” in place of Electrical Installation Certificate
The use of incorrect terms to describe the Earthing Conductor and Main Equipotential
Bonding Conductors and to identify protective conductors connected to the MET(main
earthing terminal), were typical errors.
The testing of an ‘open loop’ was often used when describing how to establish R1 + R2
which could imply the circuit is incomplete
Students referred to ‘a schedule of tests’ rather than the Schedule of Test Results.
Basic knowledge
Some Students were unable to state the need for an Electrical Installation Certificate and
very few were able to identify who is responsible for comparing test results and why.
Understanding this is a fundamental requirement for someone who is studying in this
subject area.
It appears that Students have forgotten that 1 MΩ is the minimum acceptable value of
insulation resistance for a circuit and appear to have adopted 2 MΩ as the new value.
Students often lost marks by listing the test sequence for each circuit rather
than the functional tests required, for example, operating the switches on a lighting circuit.
Naming documentation
When stating the required documentation to be completed during an initial verification of
new work, Students often omitted the Schedule of Inspections and the Schedule
of Test Results. Wrong terminology was also common with the “Schedule of Items
Inspected” and a “Schedule of Tests” being wrongly used but common alternatives.
This is also true when a Periodic Inspection Report was required. Students were unable to
identify those statutory documents which are Acts and those which are Regulations For
example, the Electricity at Work Regulations (EAWR) is not an ACT it is a regulation.

In the answers to questions relating to documentation, Students often referred to
documents that do not exist. For example, there is no ‘schedule of tests’ or a ‘Periodic
Inspection and test certificate.’
Completing documentation
The ability of Students to complete standard documents continues to be poor. Much of the
information required to be entered on documents was often omitted. It would appear from
the attempts by some students that they were not familiar with these standard forms.
One question required a Schedule of Test Results to be completed for the two new ring
circuits.
Some responses included a lighting circuit while others gave no information relating to the
circuit conductors.
Another error involved entering the maximum values of Zs in column 12. No functional
tests recorded, no indication that the continuity of ring final circuit test had been completed
successfully and the lack of recording the type of supply and values of Ze and PFC were
other common errors.
Describing test procedures
When describing how to carry out a test, students were often confused as to what was
required, were unable to describe a logical approach and rarely used large clear diagrams
to assist with their description, even when the question requested this.
Practice of these skills during their course would greatly improve the quality of their
answers.
A significant number of answers included dangerous procedures and the use of
inappropriate instruments which, if applied, could have resulted in serious injury.
Answers of a dangerous nature result in no marks being awarded, So remember
permission to isolate, inspect no risk to people property or livestock isolate, lock off, verify
isolation and always select and state the name of the correct meter and in some
circumstances the standard the meter/ leads have to follow (GS38).
Students often forget to seek permission to isolate, and indeed many do not even
mention isolation. Other areas often neglected in answers are the use of GS 38 test leads,
placing links if required, actually connecting the test instrument, recording results and
reinstating the circuit on completion. A large majority of Students stated that the test button
on an RCD is the essential test that must precede the testing of an RCD. This is not the
procedure given in Guidance Note 3. This needs to be explained to Students.

Test values
Many Students were unable to identify correct test values, acceptable test results and the
actual test current to be applied for RCD testing.
One question asked for appropriate scales for given tests. Many Students did not
differentiate between the scale values for earth electrode resistance and continuity of
protective conductors (both given as Ohms).
Where scale values are requested the responses should indicate suitable scales, for The
Question above should have been answered with values of 200 Ω and either low ohms or
>2 Ω would be appropriate.
Calculations
Many Students had problems with calculations related to the inspection and testing
process.
Cumulative IR, resistors in parallel calculations
Calculation of R1 andR2 when given values for Zs and Ze.
These were related to the typical calculations which may be required during the verification
of test results. As these are fundamental to the activities of initial verification and periodic
reporting such calculations should be within the capabilities of the Students.
Exam technique
Students should spend one minute on an answer for each possible mark to be awarded.
For example, a three mark question should take approximately three minutes
to complete, although many questions in Section A will take considerably less than this.
Many Students still use paragraph text to describe procedures rather than use bullet
points. The bullet point approach saves Students’ time and will help them to review their
answers for accuracy.
Careful reading of the question is important. Too many answers did not include the
requested information. For example, the answer to one question required a list of the first
four tests, including instruments, to be carried out on a lighting circuit and two ring circuits.
Often no instruments were quoted and in some cases Students merely reproduced the
standard list of tests in its entirety.
Many Students did not answer the questions in Section B of the paper in relation to the
given scenario and this often resulted in the loss of marks. Students must read the
information carefully and use this in conjunction with the information given in the question.
It may be helpful if students were encouraged to highlight key information in the scenario
as they read it, so that they will become more aware of this as they attempt the questions
in this section.

Question 1 required the student to identify the three types of work for which an EIC would
be issued ‘as identified on the Electrical Installation Certificate’. The majority of Students
identified three forms of certification (EIC, MEWC and PIR) not the three types of
installation work identified on the EIC. New installation, Addition to an existing installation
and alteration to an existing installation.
Question 2 required the student to describe the process for testing continuity of ring final
circuits. Very many Students were unable to describe the process of ring circuit continuity
testing. Many failed to carry out both stage 2 and stage 3, were unable to detail what
information was obtained and expected values. Very few provided drawings as requested.
Question 3 required the student to describe the correct procedure for carrying out an
insulation resistance test on car park lighting columns. Students were generally unable to
correctly describe the testing process with the isolation of columns and testing distribution
cables and then connecting P&N and testing between P&N to E for the columns. Few
Students were able to provide reasons for the use of larger cables than those required to
meet the current carrying requirements.
Question 4 required Students to identify the tests which would need to be carried out
during a one hour period, the only time when the whole installation could be isolated. Most
Students reproduced the sequence of test without any consideration for the situation.
Indeed most Students, judging by their responses, would carry out the complete periodic
inspection and test of the visitor centre in one hour.
Question 5
a) required Students to provide diagrams of the MET (main earthing terminal) with all
associated protective conductors
In the response many Students did not correctly identify all the items which required main
equipotential bonding conductors and failed to correctly identify those conductors which
they did show.
b) a fully labelled earth fault loop path for the 1st car park light.
In the responses to b) many failed to show the correct system. Of those who did produce a
TT system many failed to correctly identify the relevant component parts, earthing
conductor, general mass of earth, MET, R1 and R2 etc.
Question 6 required Students to list, in the correct sequence, the first three tests to be
carried out on a newly installed lighting circuit. Many Students were unable to do so. The
correct titles were not given, the wrong order was stated and including a ring final circuit
continuity test in the sequence were typical errors.

Question 7 requested the identification of three special locations as identified in Part 6 of
BS 7671 in the 16th edition part 7 in the 17th edition , in addition to bathrooms, shower
rooms, saunas and swimming pools. A surprising number of Students were unable to give
three suitable answers. Many gave inappropriate installations identified in Part P of the
Building Regulations while others named installations at random such as petrol stations.
Question 8 required the student to state why the rule of thumb is applied when assessing
the earth loop impedance test result of a circuit. Many Students were unable to offer a
suitable explanation, often stating that it was easier than using more detailed calculations
or “because of temperature”.
Question 9 gave three insulation resistance test results and the student was requested to
identify the circuit condition revealed. Surprisingly, some students stated that 0.00 MΩ
indicated an open circuit.
Question 10 required Students to determine whether measured values of earth loop
impedance for a number of circuits were acceptable. Many answers applied the “rule of
thumb” to the measured values and not to those given in BS 7671. Details of the
necessary calculations were often omitted even though the question requested Students to
show all calculations.
Question 11 of the paper required the student to describe the correct procedure for
carrying out an insulation resistance test on a lighting circuit. Many Students did not state
the instrument to be used, the test voltage and the acceptable test value. Often key
procedural information was not included, operation of two-way switches and disconnection
of loads being typical examples.
Question 12 required the student to describe the process for testing external earth loop
impedance. Some answers stated that it was a live test and then stated the phase (now
line conductor) and cpc were to be connected together. Other answers included the
removal of the earthing conductor while all circuits were energised. Many did not specify
the use of leads to GS 38 and the disconnected earthing conductor was often not
reconnected.
Question 13 required the student to describe the correct procedure for carrying out an
RCD test. Once again guidance was given in the question to help Students include all
relevant details. Often Students did not state the exact test current values, even though
this was clearly requested.
Question 14 asked ‘who is responsible…’ Students saw the word ‘responsible’ and started
referring to the ‘duty holder’ or ‘competent person’. Although the person should be
competent and may well be the duty holder, the student was expected to identify that it
was the person carrying out the inspection.

Question 15 asked Students for the reason why periodic inspections and tests are carried
out in accordance with BS 7671. Few Students stated that it was to determine if the
installation was safe to stay in service. Most decided the question was asking for a list of
reasons or circumstances such as ’the time is due’ or ‘insurance purposes.’
Question 16 required the Students to provide information regarding GS 38 and clearly
stated ‘in addition to items relating to leads and probes.’ Students saw GS 38 in the
question and answered with ‘4mm or fused probes etc.’ Students did not answer the
question asked of them.
Question 17 had the word ‘polarity’ in it. Many Students used ‘ES lamp holders’ and the
like as answers. The question was not asking for examples but the reasons for a polarity
test.
Question 18 asked for a list of tests required, including the instrument and instrument
range in each case. A large majority of Students did not include the ranges required,
resulting in valuable marks being dropped.
Question 19 required Students to identify the instrument and unit of measurement used
when carrying out a test of continuity of protective conductors which many Students
correctly identified.
A large number of Students were unable to state why the particular instrument was used
as required. Typical common errors were that the instrument did not produce a high
voltage, so no risk of shock, or that the instrument would not damage equipment.
Question 20 required Students to state, using the correct terminology, three protective
conductors connected to the main earthing terminal. A large number of Students used
incorrect terminology and common errors included supplementary bonding, lightning
conductors, main earth bonding and earthing to services.
Question 21 related to the reasons for the ring final circuit continuity test. Many Students
were unable to identify the reasons for the test and so were unable to demonstrate their
understanding of the need for the process. A large number of Students identified the
recording of R1 + R2 and/or Polarity neither of which are the reason for the test but are
actually obtained as a consequence of the test.
Question 22 - Very few Students were able to correctly identify the use of the X in the IP
code references, far too many believed that there was no protection offered for the
particular protection item. A surprising number still do not appreciate the significance of the
code in regards to the level of protection is offered.
Question 23 - Many Students were unable to state two methods of confirming compliance
of measured Zs with the requirements of BS 7671. Common responses included,
calculation, measurement, multiply by 0.75 (but not what was multiplied) and enquiry.

Question 24 - Many Students confused prospective fault current with prospective earth
fault current. Consequently their answers were not correct as they would test for pfc and
pscc then record pfc on the certificate.
Question 25 - A large number of Students, in fact far too many, responded that the
measurement of pfc was related to the disconnection time of the device. Too few identified
the relationship to max fault current rating of protective devices.
Question 26 - Many Students incorrectly stated that the inspector was responsible for
determining the period to the first periodic inspection.
Question 27 - Many Students stated that the core of the swa could not be used as a main
equipotential bonding conductor giving reasons such as it was not continuous, not
connected at the MET or not 10mm2. Many of those who identified it as acceptable related
the size of the conductor to the live conductors in the swa, not the incoming supply. For
part d a large number of Students failed to identify the presence of the armour in parallel,
giving parallel paths through main equipotential bonding as the reason. Many Students
incorrectly identified the difference as being due to the temperature between the R1 + R2
test and the Zs test.
Question 28 - A large number of Students were unable to determine the expected overall
insulation resistance of the installation. Many suggested that it would be equal to the circuit
insulation resistance, ie 200MΩ, a number decided that it would be 14 x 200MΩ and
others 0.07MΩ.
Question 29 - The majority of Students forgot to include the R1 + R2 value for the
distribution circuit in their calculation for the lighting circuit Zs.
Question 30 - A number of Students were unable to correctly indicate the system used for
the scenario and so losing a considerable number of marks. Many Students stated that the
pfc would be higher at the new distribution board “because it was further away”. A large
number of Students stated that the Pfc was measured to confirm disconnection time. From
these two typical incorrect responses it would appear that Students were unable to
distinguish between Pfc and earth fault loop impedance.
Question 31 required a suitable test method for the continuity of protective conductors for
the distribution circuit. Despite this being 30m from the main intake position and
terminating in a remote building, a number of Students opted to carry out the test with a
wander lead.
Question 32 was very poorly answered. The procedure for testing ring final circuit
continuity has appeared in one form or another in recent papers. A large number of
Students were unable to correctly describe the process and many indicated a total lack of
understanding of the procedure. Common errors being, only completing one or two parts
of the test, not cross connecting the conductors, failure to establish the expected values
correctly. A number appeared to believe that the end to end test was all that was required.

Question 33 required the student to describe the process for a direct test of the earth loop
impedance for a lighting circuit. Some answers included the removal of the earthing
conductor while all circuits were energised. Many did not specify the use of leads to GS38.
The extent of the answers given for a question part worth 9 marks was generally
inadequate.
Question 34 asked Students why the phase (line) loop + neutral loop value is divided by 4
to obtain the expected value for stage 2 of the ring final circuit continuity test.
Question 35 asked for the significance of measuring the Pfc for an installation. Many
Students related this to disconnection time or establishing an earth path exists. A large
number suggested that a protective device would not operate if its PSCC rating was too
high. Another common error was that the device would not disconnect in time if incorrectly
rated.
Question 36 required the student to describe the correct procedure for carrying out an
insulation resistance test on a lighting circuit. Students were generally unable to correctly
describe the testing process and disconnecting switches and controls without bypassing or
linking out was common. Students appear to believe that electronic equipment is simply
disconnected and not appreciating that the circuit has been broken and therefore not fully
tested. Many Students did not indicate the instrument used or any of the checks that
should be made on the test equipment before use.
Question 37 required Students to provide information on testing of 30mA RCDs. Very few
Students were able to identify the test currents applied, the need for tests at 0º & 180º and
appropriate disconnection times. A common error was stating a 200ms disconnection time
for a BS EN 61008-1 RCD.
Question 38 required the student to identify three competence requirements, given in GN3
for the Inspector. Students identified almost anything but the competence requirements
identified in GN3.
Question 39 required information relating to the ‘nature of the supply’ and most Students
failed to provide the items listed in IEE regs (16th edition) 313-01-01 or IEE regs (17th
edition) 313.1 with the type of earthing arrangement being a common error.
Question 40 asked when the inspection and testing of a new installation would be carried
out. Many Students related their answer to periodic inspection requirements.
Question 41 asked for three items to be inspected during the first fix of a pvc conduit
installation. Many Students missed the reference to the conduit system and gave cable
compliance requirements.

Question 42 - Many Students related their answers to a periodic inspection or an extension
to an existing installation despite the information given in the scenario. Students were
required to identify all the documents that would be issued for this installation and the
majority failed to identify the need for more than one set of schedules for the installation.
Question 43 - Many Students were unable to correctly produce a diagram of the correct
earth fault loop path. Despite the question clearly stating ‘fully labelled’ many failed to label
their attempts. A large number failed to provide a complete path, omitting the supply
requirements some showing the system finishing at an installation electrode. A disturbing
number failed to isolate the pitch supply sockets from the TN-C-S earthing arrangement
connecting an electrode to the MET for the TN-C-S. A number of Students thought that the
fault current flowed to earth and then stopped!
Question 44 - Most Students, but not all, were able to identify whether the readings for
tests two and three were acceptable or not. Very few were able to give any realistic
reasons for the readings obtained. Conductors not connected, which was negated by the
values from test one. Where an incorrect polarity was identified this was often given
between the incorrect conductors or simply stated as ‘incorrect polarity’. In general
Students demonstrated they were aware of what was expected but had no understanding
of why and could not identify problems. This would support a lack of experience for many
Students.
Question 45 - Part c most Students provided a calculation for each circuit and gave this as
their answer. The question relates to the minimum breaking capacity of circuit breakers
fitted in a distribution board at the origin. The prospective fault current was therefore the
Pfc at the distribution board supply, not each circuit. When considered with the responses
to question 45 it is evident that the majority of Students have no understanding of
prospective fault current and its implications for the installation.
Students were unable to demonstrate an understanding of the requirements for the
preparation for inspection and testing, statutory requirements and BS7671.
Students should be advised to use drawings to help illustrate their answers, even where
this is not requested in the question. If it helps the student to clearly describe their answer
and reduce the amount of descriptive narrative required this will benefit the student in both
clarity of the answer and time taken.

2330 level 3 unit 2

2011-07-12T04:15:00.000-07:00

unit 2 inspection testing and commissioning

this is a written test and consists of 12 questions
all questions are worth six marks
on exam day you will need atleast 50 marks to gain a pass, so what are you waiting for, get practicing and be ready for D day ;-)

1)
list three widely used tyres of

a wiring sysytem

b wiring enclosure

2)
when making an area safe to work in

a list 3 procedures to be taken before commencing work

b describe the permit to work procedure

3)
when carrying out large contracts

a list three parties likely to be concerned

b state the perpose of a site record

4)describe the use of the following in monitoring the progress of a contract

a a bar chart

b a site diary

c variation order

5) with the reference to the application and the use of residual current devices (RCD)

a list three situations where RCD protection is required

b state the primary function of an RCD

C describe the term nuisance tripping

6)

a explain briefly the importance of a verification of test instruments before performing tests on an electrical installation.

b state the purpose of each of the following types of test instrument

i) insulation resistance tester
ii) tong tester
iii) pscc tester
iv) low ohms meter

7) a 10kW230v shower is supplied using PVC/PVC multicore cable clipped direct to the surface over a distance of 15m. the circuit is protected by a BSEN 60898 type C circuit breaker , the ambient temperature is 25 deg C

determine

a installation method

b design current

c circuit breaker rating

d correction factor

e minimum cable size

f voltage drop

8)
identify three items to be checked during the initial inspection progress for -

a steel conduit

b steel trunking

9)
when completing addititons to a circuit such as an extra socket

a state the type of certificate to be used

b list three item of information that need to be entered on the form

c state to who the form should be given

10)
describe breifly the purpose and types of information which relate to the electrical installation of the following types of drawing

a site plan

b block diagram

c circuit diagram

11)
a explain the importance of coordinating electrical installation contracts with other trades

b describe one example where joiners/ carpenters may be held up due to lack of coordination with electricians working on the same site

c describe one example where plasters may be held up due to lack of coordination with electricians working on the same site

12)
a with the aid of a sketch , show how a 230v single phase supply and a 400v three phase supply is achieved within a sub-station using a transformer with delta connectedn11kV primary windings and the star connected secondary windings
4 marks

b state two reasons for balancing the loads across a three phase four wire system
2 marks

2330 level 3 unit 1 questions

2011-07-11T05:59:00.001-07:00

2330 level 3 revision

unit 1 application for health and safety
1)
the health and safety at work act sets a framework stating how:
a) employers must safeguard the health and safety of there employees
b) employees can claim compensation for accidents at work
c ) to work in dangerous situations without using personal protective equipment
d ) employerscan reduce their responsibilitys for health and safety

2)
when personal protective equipment ( PPE) is provided by an employer it is the responsibility of the employee to:
a) report damaged ppe to the health and safety executive
b) inspect ppe before and after use
c) wear damaged ppe if replacements are not available
d) pay for repairs to damaged ppe

3)
a sign displaying a white pictogram on a circular blue background is a
a) safety sign
b) mandatory sign
c ) warning sign
d ) prohibition sign

4)
a person who represents other workers on safety matters in an organisation is called a:
a) safety officer
b) safety representative
c) health care representive
d) health and safety officer

5)
accidents in the workplace can be reduced by providing
a) more first aid centres
b) clearly marked exit signs
c) safety education and publicity
d) more fire extinguishers
6)
carrying out a survey of the workplaceand preparing a report on potential health hazards is called a:
a) risk survey procedure
b) risk assessment procedure
c) health procedure assessment
d) health survey procedure
7)
development of new technology in the electro technical industry will require:
a) a need for continual retraining
b) a need to employ younger staff
c) employees to move into less skilled jobs
d) employees to prepare for redundancy

8)
the term that is used to describre the satisfactory performance of equipment is:
a) performs well at all times
b) fit and performs for the guarantee period
c) fit for purpose intended
d) performs without maintenance

9)
a permit to work procedure must be issued by
a) a qualified first aider
b) the health and safety executive
c) a suitable responsible person
d) the safety commitee

10)
employees should not wear ties or loose clothing when working :
a) in any part of a factory
b) in confined spaces
c) with toxic materials
d) with rotating machinery

11)
to provent the risk of electric shock when working on an electric motor, the motor should be isolated from the supply by:
a) opening and locking off the isolator
b) pressing the emergency stop button
c) pressing the stop button on the starter
d) disconnecting the whole installation from the supply

12)
a colleague receives an electric shock which results in unconsciousness. the first action to be taken is to:
a) shake the person by the arm
b) walk and find the first aid officer
c) dial 999 for an ambulance
d) apply resuscitation techniques

13)
a gas which is heavier than air and can cause an oxygen deficiency in confined spaces leading to asphyxiation is:
a) nitrogen
b) methane
c) hydrogen
d) helium

14)
a fault occurring on equipment in the work place with the potential of causing harm to employees is termed:
a) a hazardous malfuction
b) an industrial malfunction
c) a maintenance fault
d) a workplace danger

this page in a work in progress more questions to follow shortly, in the meantime you might like to check out the following link which covers all the key points required to pass the 2330 level 3 exam

unit 1 applying health and safety procedures and electrical principles,

unit 2 installation ( buildings and structures) inspection and testing and commissioning,

unit 3 fault diagnosis and rectification.

there are sample questions with answers for you to practice ready for your exam.

thanks for looking at my page i hope you found it useful, please share your thoughts by leaving a comment, check back soon for more updates , many thanks

17th edition questions

2011-07-11T05:07:00.000-07:00

2382 -10
17th edition sample questions

1 ) to which of the following electrical installations does the iee regulations NOT apply ?
a agricultural and horticultural premises.
b construction sites
c systems for transmission of energy to the public
d caravans and their sites

2) the BS 7671 relates to permanent and temporary installation for
a equipment on board ships
b aircraft equipment
c contruction sites
d electric traction equipment

3) an a.c. voltage or 90v between conductors is classified as
a extra-low voltage
b low voltage
c safety extra-low voltage
d reduced low voltage

4) which one of the following types of installation is not included in the special installation recognised by the IEE wiring regulations
a swimming pools
b petrol stations
c agricultural
d saunas

5) the maximum accessible distance that it should be assumed a person can reach when standing on a surface is
a 0.75
b 1.25
c 2.50
d 3.00

6) BS 7671 requires that the designer of a new installation shell
a have atleast three years experience
b recommend future inspection and testing
c complete a periodic test report
d have a copy of BS 7671

7) non sheathed cables for fixed wiring, other than protective conductors, should always be installad in
a dry conductors
b trenches
c conduit or trunking
d sub- zero temperatures

8) a final circuit is the wiring between the
a main cut-outand the energy meter
b main switch and the distrubution board
c distrubution board and current using equipment
d consumer's main earth terminal and circuit protective device

9) the prospective short circuit current at the origin of the consumer's installation must be taken into account when
a estimating the external earth fault loop impedance
b applying diversity factor for the installation
c selecting the system of earthing for the supply
d selecting the type of overcurrent protective device to be installed

10) a system is defined as
a the kWh meter and an installation
b the distubution cables to an installation
c the consumer's terminals of an installation
d a single source of energy and an installation

this page is still in progress more questions with answers to follow shortly, in the meantime you might want to check out the following links for some useful revision books covering 2391 exam success and 2382 17th edition exam success, thanks for taking the time to visit my page, and i hope you found it useful, please share your thoughts by leaving a comment below, many thanks

2391 questions

2011-07-10T12:23:00.001-07:00

1)
indicate three main items for for which you would require relevant information about in order to undertakean initial inspection on a new installation

2)
state releveant documentation that relate to the inspection and test of a system name on statutory and two non statutory

3)
an electrical installation certificate and a periodic inspection report should be accompanied by two other documents what are they?

4)
state three areas of inspection you would check when carrying out a periodic inspection report

5)
state three human senses used when carrying out periodic inspection report

6)
list the instruments which provide the measurements 20 megohms , 8KA and 22mS

7)
insulation resistance testing requires different test voltages for certain circuits, identify what circuits require the following voltages 250v, 500v, 1000v.

8)
state the first three tests that should be taken during the initial verification of a new installation.

9)
the test for continuity of the CPC in a radial circuit with one socket requires a link and a milli-ohmmetrer state: were link is connected, state where meter is connected, what the meter reading represents.

10)
state three different protective conductors that need to be connected to the main earth terminal

11)
the following results were obtained during the initial test on a healthy ring circuit
what readings would you expect after cross connection between line and neutral at each socket , between line and cpc at each socket, what does the line and cpc represent ?

12)
state the effect on conductor resistance when cable length increases
conductor resistance when CSA increases

13)
state three precautions to be taken before an insulation resistance test on a circuit

14)
an inclosure has been fabricated on site state the IP rating , it is not affected by liquids

15)
state the protection offered by the following IP ratings IP4X, IPX8, IPXXB

16)
state three reasons for conducting polarity checks on a circuit

17)
ID earthing system that is connected with overhead cables, a multi core supply cable with seperate earth and neutrel, supply in which earth and neutrel are performed in one conductor

18)
state three locations where additinal requirements for an electrical installation are needed

19)
from the formula Zs = Ze +(R1 + R2) x 1.2 x L / 1000 state what is Ze, R2 and 1.2

20)
state three functonal test to be carried out on an installation

this page is still in progress more questions with answers to follow shortly, in the meantime you might want to check out the following links for some useful revision books covering 2391 exam success and 2382 17th edition exam success, thanks for taking the time to visit my page, and i hope you found it useful, please share your thoughts by leaving a comment below, many thanks

Guidance Note 3: Inspection & Testing