BUILDING SERVICES

Wiring lampu spot light n armour cable ktc 3

noreply@blogger.com (buildingservices) — Mon, 22 Jun 2020 05:56:00 +0000

plastering

noreply@blogger.com (buildingservices) — Tue, 22 Oct 2013 23:53:00 +0000

lighting contactor wiring digram with photocell

noreply@blogger.com (buildingservices) — Tue, 22 Oct 2013 07:16:00 +0000

source from : www.google.com

circuit diagram no 368 kulim utama

noreply@blogger.com (buildingservices) — Tue, 22 Oct 2013 07:04:00 +0000

Pemasangan Water Heater Di No 1734 Taman Kulim Utama Fasa 2

noreply@blogger.com (buildingservices) — Tue, 22 Oct 2013 06:59:00 +0000

Db board problem taman kenyalang kulim

noreply@blogger.com (buildingservices) — Tue, 22 Oct 2013 06:57:00 +0000

Db board problem...alhamdulilah hampir 4 jam trouble shoot ....succes
1. Neutral earth shorted
2. Live neutral shorted

Kerja - Kerja Wiring di Taman Kulim Utama No 43

noreply@blogger.com (buildingservices) — Tue, 22 Oct 2013 06:54:00 +0000

Langkah-Langkah Awalan Untuk Memasang Air Cond 1HP

noreply@blogger.com (buildingservices) — Fri, 24 Sep 2010 04:23:00 +0000

Salam Aidilfitri, kebiasaannya kita pasang indoor unit dulu,drill lubang frame indoor unit system dulu, nak selamat water level tools, Angkat Indoor Unit untuk pasang pada frame yang kita pasang td, jangan lupa masukkan apa2 tali@kabel, untuk memudahkan masukkan kabel three core nanti....Kalau kita pasang air cond back to back, ia agak mudah, sebab paip (3" dan 1") mudah sikit...kalau jauh dinding rumah kena tebuk la pula, guna drill hammer..lagi satu untuk memudahkan pergerakan air outlet air cond, pasang indoor unit senget sikit itu jaa....lebih kurang selesai untuk indoor unit....tunggu untuk Outdoor System La pula....nak pasang outdoor system agak rumit sikit, yang pertama kita kena pasangkan L shape dulu untuk letak Outdoor nanti, kebiasaanya untuk L shape kita tebuk 4 lubang sebabnya out door berat, kita guna drill hammer, wall plug, water level tool dua jenis kecik satu (ada Magnet) dan panjang satu . siap saja L shape di pasang atau di lekatkan pada dinding luar rumah, barulah bawa naik Outdoor system, hati2 berat2 tuan....psg skru bawah outdoor system, selalunya ada empat, tibalah masa yang agak mencabar, kena buat flaring pada tiub 3 hun dn 1 hun, ati2 buat flaring takut bocor nanti, pasang atau sambunagkan paip td pada piping dekat outdor guna spanar boleh laras, selesai pasang couple tersebut, baru boleh dikatakan sempurna talian paip air cond....rehat lima minit jap, ambil meter gauge kabel warna biru di sambungkan injap masuk low pressure pada Outdoor Unit, pipe tgh atau pipe warna kuning pada "Meter Gauge" disambungkan pada pam vakum, proses ini di lakukan untuk membuang udara dalam talian paip unit air-cond, AWAS ini penting, untuk memastikan air cond boleh tahan lama, TARRRBAIK.....Buka injap Meter Gauge ke tanda kosong atau 30....hidupkan pam vakum selama 5 minit@10minit....selesai dalam tempoh 10 minit matikan pam vakum, baru buka injap pada pam vakum....tutup kembali injap meter gauge....kalau jarum naik ke atas, maknanya masih ada udara dalam talian paip, kalau udara masih ada, lakukan proses vacum sekali lagi sampai hilang udara dalam talian paip.....selepas ini kita buat proses purging pula untuk memastikan membuang udara dalam talian paip lagi, proses kita buat untuk buka gas dalam compressor..buka injap guna air linki pada LOw Pressure buka injap 1 1/2 pusingan , lepas tu purging, kebiasannya kita buat sebanyak dua kali....lepas injap tersebut kesemuanya, injap high pressure buka terus ja.....dah abis tuan.....turun tangga la tuan....sediakan three core kable untuk buat sambungan di antara indoor dan out door, maka lengkaplah sudah aircond tuan.....boleh "on" air cond tuan....selamat mencuba, tp sebelum pasang air cond sendiri, belilah peralatan dulu tuan2......

Kaedah Pemasangan Asas Bagi Sesebuah Penyaman Udara

noreply@blogger.com (buildingservices) — Tue, 11 Aug 2009 03:15:00 +0000

Kaedah Pemasangan Asas Bagi Sesebuah Penyaman Udara

Step 1:

Buat Flushing bagi mengeluarkan lembapan dalam sistem perpaipan unit penyaman udara (cooling coil)

Step 2:

periksa kebocoran pada injap servis unit air cond, dengan menggunakan spray detector.

Step 3:

buka injap servis pada high pressure dan low pressure dengan menggunakan kunci allen.

Step 4:

hidupkan unit penyaman udara.

Step 5:

Selepas 5 minit, unit air cond berfungsi, gunakan manifold gauge untuk menentukan nilai isipadu gas bahan penyejuk dalam compressor (60-80 psi)....pastikan ampere masukan bagi pemampat, bersesuaian pada manual air cond tersebut. Gunakan Clamp Meter untuk mendapatkan bacaan ampere tersebut...

Semoga Berjaya...sejuk

HEAT TRANSFER

noreply@blogger.com (buildingservices) — Mon, 09 Mar 2009 16:26:00 +0000

Heat is a form of energy and can be defined as energy that transmits from one body to another as the result of a temperature difference between the two bodies. All the other energy that is transferred occur as work.

Heat transfer takes place from a highes temperature to a lower temperature (from a warm body to a cold body) and never in the opposite direction. Since heat is energy, it is not destroyed or used up in any process. The rate of heat transfer is always proportional to the difference in temperature that is causing the transfer. The transfer of energy as heat occurs in three ways :
i. By conduction
ii. By convection
iii. By radiation

LATENT HEAT

Latent heat is the process whereby heat is added but there is no rise in temperature. An example is when heat is added to water while it is boiling in an open container. Once water has reached the boiling point, adding more heat only makes it boil faster, it does not raise the temperature.

SENSIBLE HEAT

When a change of temperature can be measured by thermometer and the level of heat or heat intensity has changed, it is called sensible heat.

SPECIFIC HEAT

The specific heat (c) is the amount of heat necessary to raise the temperature of 1lb of a substance to 1˚F. Every substance has a different specific heat. For example, the specific heat of water is 1Btu/lb ˚F , where as the specific heat of ice is 0.5 Btu/lb ˚F.

CALCULATING HEAT QUANTITY OF HEAT

From the definition of specific heat, it is evident that the quantity of heat energy supplied to, or given up by any given mass of material to bring about a specified temperature change can be determined from the following relationship :

Q = (m) (c) (T2 – T1)

Where Q = The quantity of heat energy in British
Thermal Units (Btu)
m = The mass in pounds
c = The specific heat in Btu per pound per degree Fahrenheit
T1 = The initial temperature in degrees Fahrenheit
T2 = The final temperature in degrees Fahrenheit, consistent with T1

CORROSION

noreply@blogger.com (buildingservices) — Mon, 09 Mar 2009 16:21:00 +0000

A simple definition of corrosion is the deterioration of a material or its properties due to the reaction with the environment. Sometimes the deterioration is a weight gain; sometimes it is a weight reduction and sometimes the mechanical properties are affected. Most corrosion processes are electrochemical in nature.

TYPES OF CORROSION

Uniform

The simplest form of corrosion is a uniform attack of all surfaces that are exposed to a corrodent. It can be electrochemical in nature or simply a direct attack.

Pitting

Pitting is a local corrosion damage and caused is by the chemical nature of environment. Solutions that tend to produce pitting are brackish water, salt water, chloride bleaches, and reducing inorganic acids. Certain metals such as stainless steel are particularly prone to pitting attack.

Crevice Corrosion

Crevice corrosion is a local attack in a crevice between metal to metal surfaces or between metal to non metals surfaces. One side of the crevice must be exposed to the corrodent and the corrodent must be in the crevice. Crevice corrosion commonly occurs in poorly gasketed pipe flanges and under bolt heads and attachments immersed in liquids.

Dealloying

Dealloying is a process whereby one constituent of metal alloy is removed from the alloy, leaving an altered residual microstructure. The most common alloy susceptible to this process is yellow brass. The removal of zinc from brasses is called dezincification.

CORROSION CONTROL

The use of existing corrosion data is the first step in solving corrosion problems or preventing potential corrosion problems. To simplify the subject of corrosion control, there are three factors that have equal weight in importance : material selection , environment control and design.

STRESS, STRAIN, HOOKE’S LAW, AND MODULUS OF ELASTICITY

noreply@blogger.com (buildingservices) — Mon, 09 Mar 2009 16:17:00 +0000

STRESS, STRAIN, HOOKE’S LAW, AND MODULUS OF ELASTICITY

INTRODUCTION

Structural materials used in Mechanical and Civil Engineering practice must generally have strength. What is strength ? Strength is due to the sum of forces of attraction between negatively charged electrons and positively charged protons within the material. When covalent bonds join large numbers of atoms to produce giant molecules as is the case of the carbon atoms in carbon fibre, the strength of the resultant material is great.

Constructional materials generally must be able to withstand the action of considerable forces without undergoing other than very small amounts of distortion. Materials must be capable of permanent deformation at the expense of as little energy as possible. That is, it must be malleable and ductile.

Malleability refers to the extent to which a material can undergo deformation in compression before failure occurs, whilst ductility refers to the degree of extension which takes place before failure of a material in tension. All ductile materials are malleable but malleable materials are not necessarily always ductile since a soft material may lack strength and those tear a part very easily in tension. Other mechanical properties include elasticity, hardness, toughness and also creep and fatigue properties. In each case, the property is associated with the behaviour of the material toward the application of force.

DEFINATION OF STRESS

When a force is transmitted through a solid body the body tends to undergo a change in shape. This tendency to deform is resisted by the internal resilience of the body and the body is said to be in a state of stress. Thus, a stress may be described as a mobilized internal force which resists any tendency towards
deformation. The definition to describe the force transmitted per unit area as the intensity of stress or unit stress.
Stress ‘a measurement of density of forces’ is defined as force per unit area of cross section. The Standard Imperial (SI) unit of stress is the Pascal (Pa) which is equivalent to a force of one Newton acting on an area of one square metre, i.e. N/m2 or Nm-2. Numerically it will be the same as that expressed in Mega Pascal (MPa).

All materials bodies will deform when placed in a state of stress, and as the stress is increased the deformation also increases. In such cases, when the loads causing the deformation are removed, the body returns to its original size and shape. A material or a body having this property is said to be elastic. It is also noticeable that if the stress is steadily increased, a point is sooner or later reached when, after the removal of the load, not all of the induced strain is recovered. This limiting value of stress is called the elastic limit.

STRAIN

When a force is transmitted through a solid body the body tends to be deformed. The measure of this change in shape is called strain. When a body is placed in a state of stress it undergoes strain according to the configuration of the stress applied. Thus, direct stresses cause changes in length or shearing stresses cause twisting and bearing stresses cause indentation in the bearing surface.

Strain refers to the proportional deformation produced in a material under the influence of stress. It is measured as the number of metres of deformation suffered per metres of original length and is a numerical ratio.
Strain may be either elastic or plastic. Elastic strain is reversible and disappears when the stress is removed. Strain is roughly proportional to the applied stress

HOOKE’S LAW

The relationship between the induced strain and stress causing it is found to be constant in elastic materials. Hooke’s Law defines that ‘strain is proportional to the stress causing it, providing that the limit of proportionality has not been exceeded’.

Modulus of Elasticity (Young’s Modulus),E

Young’s Modulus of Elasticity (E) is the ratio between the stress applied and the elastic strain it produces. That is, it is the stress required to produce a unit quantity of elastic

strain. It is related to the rigidity of the material. The modulus of elasticity is expressed in terms of either tensile or compressive stresses and its units are the same as those for stress.

MATERIAL PROPERTIES

noreply@blogger.com (buildingservices) — Mon, 09 Mar 2009 16:09:00 +0000

MATERIAL PROPERTIES
SOLIDS, LIQUIDS, GASES AND PLASTIC (POLYMERIC)

INTRODUCTION

Since the earliest days of the evolution of mankind, the main distinguishing feature between human beings and other mammals has been the ability to use and develop materials to satisfy our human requirements. Woven cloths took the place of animal skins and manufactured goods became increasingly more sophisticated. Nowadays we use many types of materials, fashioned in many different ways to satisfy our requirements for housing, heating, furniture, clothes, transportation, entertainment, medical care, defence and all the other trappings of a modern, civilized society.

Engineers can play an important part in this conservation of material resources by a understanding of the materials used. This understanding is necessary in order to enable them to select the most appropriate materials and to use them with the greatest efficiency in minimum quantities whilst causing minimum pollution in their extraction, refinement and manufacture.

SOLIDS, LIQUIDS AND GASES

Most substances can exist as solids, liquids or gases depending upon their temperature. A notable exception is iodine which sublimes directly from the solid state into the gaseous state when heated without becoming a liquid. Most substances behave like water. Below its freezing point water is a solid (ice). Above its freezing point and below, its boiling point is in the liquid state. If its temperature is increased still further it boils and becomes vapour (steam) before turning into a gas with further heating.
The fact that a substance can exist in the solid state, the liquid state and the gaseous state is due to the fact that the atoms and molecules of substances are in a permanent state of vibration, providing the temperature is above absolute zero (-273 oC), at which temperature, all atomic and molecular movement stops.
When the temperature is low for a given substance to be in its solid state, the vibration is of small amplitude and the atoms and molecules only move to a small extent about a fixed point. When the temperature of a solid is raised to above its melting point, the atoms and molecules of the substance vibrate more violently. They no longer move about a fixed position but are free to move about within the constraints of the container holding the liquid. Finally, if the temperature is raised still further until it is above the temperature of vaporization for substances, the atoms and molecules move so freely that
they can disperse until they completely fill the vessel containing them and if they escape they continue to disperse throughout the atmosphere indefinitely.
This is due to a change in state being accompanied by the taking in or the giving out of latent heat – that is, the heat energy associated with a change of state without an accompanying change of temperature. Heat energy which causes a change of temperature without a change of state is referred to as sensible heat.

POLYMERIC (PLASTIC) MATERIALS

There is an ever-increasing number of synthetic, polymeric materials available under the popular name of plastics. This is a misnomer since polymeric materials rarely show plastic properties in their finished condition. In fact many show elastic properties. The name ‘plastics’ comes from the fact that during the moulding process by which they are shaped, they are reduced to a plastic condition by heating them to just above the temperature of boiling water.

The properties of plastic materials vary widely depending upon composition. A snooker ball is made from hard plastic such as melamine-formaldehyde and has obviously different properties from the soft plastic insulation of a flexible electric cable. For this latter application a plastic material of very different composition is used such as polymerized vinyl chloride (PVC). There are three main groups of polymeric or ‘plastic’ materials which are :-

i. Thermosetting Plastic (Thermosets)
ii. Thermoplastic
iii. Elastomers

Thermosetting Plastic (Thermosets)

This group of polymeric materials undergoes chemical change during the moulding process and can never again be softened by reheating. These materials are generally hard, rigid and rather brittle. A typical example is melamine formaldehyde used for making such articles as snooker and billiards balls, table-wear and domestic electrical fittings. The strength of thermosetting plastics can be greatly increased by reinforcing them with fibrous materials.

Thermoplastic

These become soft and can be remoulded each time they are reheated. They are not so rigid as thermosetting plastics but tend to be tougher. For example, rigid polymerized vinyl chloride (PVC) is used for rain water guttering and down-piping on buildings. Thermoplastics can also be soft. For example, the non-rigid PVC is used for the insulation of flexible cables.

Elastomers

The elastomer, or rubbers are cross-linked polymeric materials in which they are not in sufficient to make them as rigid as the thermosetting plastics, but one just sufficient to make them return to their original dimensions when the deforming load is removed. Elastomers are usually addition polymerized as thermoplastics and then vulcanised with sulphur at approximately every five-hundredth carbon atom. Increasing vulcanization is increase the stiffness and reducing the elongation properties of the materials.

Sanitary pipe work

noreply@blogger.com (buildingservices) — Tue, 03 Mar 2009 16:43:00 +0000

Sanitary pipe work is a system of pipes installed to permit the transfer of waste water and sewage from building to foul drain. Also it provides a means of ventilation for that drain so that there can be no build up unpleasant odors or methane gas within the system which might accidentally permeate into the building. For efficient working of a disposal installation pipe work system, a number of design criteria should be fulfilled.
In the following section we will look at some of the terms related to sanitary pipe work.

DEFINITION OF TERMS

Soil Waste
This is discharged from water closets, urinals, slop sinks and similar appliances.

Soil Pipe
This pipe conveys the discharge of water closets or fixtures with similar function, with or without the discharges from others fixtures.

SANITARY APPLIANCES

noreply@blogger.com (buildingservices) — Sun, 22 Feb 2009 06:05:00 +0000

SANITARY APPLIANCES
Fitting used for cleansing and disposing of waste product, most sanitary appliances fall into one of two groups, waste appliances ( bidets, wash basins, sinks, showers / baths tubs , drinking fountains ) and soil appliances ( water closet, urinal ). All sanitary appliances are made of non-absorbent, non-corroding, smooth and easily cleaned material and usually made from ceramic ware, vitreous enameled cast iron, vitreous enameled pressed steel, stainless steel or plastics (thermosetting and thermoplastic).

Water Closet
This is the most common type of plumbing appliance and also known as a toilet. It should be vitreous china , except in correctional institutions. It is specifically designed to accept and discharge human waste, including solids. Water closet are usually subdivided according to where they are mounted (floor mounted and wall mounted ) and how they are flushed (tank type and flush valve type ).

AIR CONDITIONING FOR LARGE MULTISTOREY BUILDINGS

noreply@blogger.com (buildingservices) — Sun, 22 Feb 2009 05:57:00 +0000

AIR CONDITIONING FOR LARGE MULTISTOREY BUILDINGS

DESIGN CONSIDERATION

Most large multistorey buildings are highly centralized air conditioning equipment. The roof and basement are the usual choice for these central station systems. The basement has the advantages of easy utility connections, noise isolation, not being valuable rental area and the fact that structural loads are not a problem. The roof on the other hand, is the ideal location for fresh air intakes and heat rejection to the atmosphere.

TYPES OF AIR CONDITIONING SYSTEMS

Large buildings have so many thermal zones, and there are so many ways to move heat from one place to another, that hundreds of air conditioning systems have been devised. One way to classify air conditioning systems is by the media used to transfer heat. Although thousands of liquids and gases can be used as carrier of heat, the three most common in building applications are air, water and refrigerant. Air conditioning for large buildings have three main system classifications:

a. All-air systems
b. Air and water systems
c. All water systems

ALL-AIR SYSTEMS

The great advantage of all-air systems is that complete control over air quality is possible. The main disadvantage is that all-air systems are very bulky and a significant part of the building volume must be devoted to them. It must be noted that for clarity only the supply ducts are shown on each plan in the following examples. Usually there is also a sizable return duct system on each floor.

AIR-WATER SYSTEMS

The following systems supply both air and water to each zone of a building. Although this increases the complexity of the mechanical systems, it greatly decreases the size of the equipment because of the immense heat-carrying capacity of water as opposed to air. Air is supplied mainly because of the need for ventilation.

AIL-WATER SYSTEMS

Since these systems supply no air, they are appropriate where a large amount of ventilation is either not necessary or where it can be achieved locally by other means such as opening windows.

Chiller

noreply@blogger.com (buildingservices) — Wed, 18 Feb 2009 05:38:00 +0000

A chiller is a machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. A vapor-compression water chiller comprises the 4 major components of the vapor-compression refrigeration cycle (compressor, evaporator, condenser, and some form of metering device).

These machines can implement a variety of refrigerants. Absorption chillers utilize water as the refrigerant and rely on the strong affinity between the water and a lithium bromide solution to achieve a refrigeration effect.

Most often, pure water is chilled, but this water may also contain a percentage of glycol and/or corrosion inhibitors; other fluids such as thin oils can be chilled as well.

AIR CONDITIONING OF SMALL BUILDINGS

noreply@blogger.com (buildingservices) — Thu, 12 Feb 2009 16:15:00 +0000

AIR CONDITIONING OF SMALL BUILDINGS

INTRODUCTION

Air conditioning systems generally have common basic elements; however, they may differ dramatically in physical appearance and arrangement. Even with the same elements present, the manner in which systems are controlled and operated may also be quite different.

COOLING SYSTEMS

To cool a building, a refrigeration made must pump heat from the variant rooms of a building into a heat sink. The heat sink is usually the outdoor air but can also be a body of water or even the ground. Cooling systems vary mostly by the way heat is transferred from the rooms to the refrigeration machine and from there to the heat sink. The choice of the heat transfer methods depends on building type and size. The four major categories ( based on how heat is transferred from building spaces to refrigeration machine) are direct refrigerant, all-air, all-water and combination air-water.

Direct refrigerant systems

The direct refrigerant system is the simplest because it consists of little more than the basic refrigeration machine plus two fans. The indoor air is blown directly over the condenser coil. Direct refrigerant units are appropriate for cooling small to medium size spaces that require their own separate mechanical units.

All-Air Systems

In an all-air system, air is blown across the cold evaporator coil and then delivered by ducts to the rooms that require cooling. Air systems can effectively ventilate, filter and dehumidify air. The main disadvantage lies in the bulky duct-work that is required.

All-Water Systems

In an all-water system, the water is chilled by the evaporator coil and then delivered to fan-coil units in each space. Although the piping in the building takes up very little space, the fan-coil units in each room do require some space.

Combination Air-Water Systems

An air-water system is a combination of the above mentioned air and water systems. The bulk of the cooling is handled by the water and fan-coil units, while a small air system completes the cooling and also ventilates, dehumidifies and filters the air. Since most of the cooling is accomplished by the water system, the air ducts can be quite small.

AIR CONDITIONING OF SMALL BUILDINGS

In smaller buildings, the heat given off by a refrigeration machine is usually dumped into the atmosphere by blowing outdoor air over the condenser coil. Medium sized building often use a specialized piece of equipment called evaporative condenser to dump heat into the atmosphere by evaporating water. Since the refrigeration lines are limited in length, an evaporative condenser cannot be more than about 60ft from the compressor and evaporator coil. Thus, for large buildings, cooling towers are frequently a better choice.

ROOM AIR CONDITIONERS

For air conditioning single spaces like motel rooms, a window unit is often used. Each of these units essentially consists of a compressive refrigeration machine. The condenser coil, compressor and one fan are on the exterior side of an internal partition. The compressor is on the outside because it is the noisiest part of the equipment. On the interior side of the partition there is the evaporator coil and a fan to blow air over it. The evaporator typically operates below the dew-point temperature of the room air for the purpose of dehumidification, so condensate forms on the coil. It drains to a pan beneath the coil . The capacity of these units may range from about 4000Btu/h (1/3 ton) to 24,000Btu/h (2 tons).

PACKAGED UNITS

Packaged units are pre-engineered self-contained units where most of the mechanical equipment is assembled at the factory. Consequently, they offer low installation, operating and maintenance costs. Usually small buildings are served by one package while larger single-storey buildings get several. Rooftop versions are the most common with each unit serving a separate zone. Packaged units are sometimes also used on the ground, for buildings with crawl spaces or above suspended ceiling when there is enough space below the roof.

SPLIT UNITS

Most homes and some other buildings find the split unit to be most appropriate. In the split unit, the compressor and condenser coils are outdoors while the air handling unit with the evaporator coil are indoors. As in all cooling systems, condensation from the evaporator coil must be drained away.

COIL BY-PASS FACTOR AND AIR MIXTURES

noreply@blogger.com (buildingservices) — Thu, 12 Feb 2009 14:34:00 +0000

COIL BY-PASS FACTOR AND AIR MIXTURES

INTRODUCTION
Cooling and dehumidification process involves not only sensible cooling but also latent removal or reduction of moisture content or dehumidification. Therefore the air will have to be cooled below its dew point temperature.

COIL BY-PASS FACTOR
In the proceeding section it is shown that the DB temperature of the air passing over a cooling coil tends to approach the surface temperature of the coil. If all the air passing through the coil come into intimate contact with the cooling surface and remains in contact with it for a sufficient length of time, the DB temperature of the leaving air could be decreased to the temperature of the cooling surface. However, as a practical matter, a certain portion of the total air quantity passing through any heating or cooling coil never comes into contact with the coil surface and therefore is unaffected by its passage through the coil. That is, it leaves the coil in the same condition that it enters the coil.

From the forgoing, it can be assumed that the air leaving the coil is actually a mixture of two air-streams or components . One component is the portion of the air that comes into direct contact with the coil surface and is assumed to leave the coil at a DB temperature equal to the mean surface temperature of the coil (line AB). The other component is the by-pass air, which does not contact the coil surface and it is assumed to leave the coil at the same DB temperature as when entering (line BC). The line AC then, represents the total quantity of the air mixture leaving the coil, which is the sum of the two component air quantities.

Since, in terms of the DB temperature scale, the length of line BC is equal to T_b
- T_c, and the length of line AC is equal to T_a
- T_c, it follows that :-

where, T_a = the DB temperature of the air entering the coil (^oC)
T_b = the DB temperature of the air leaving the coil (^oC)
T_c = the mean effective temperature of the coil surface (^oC)

The BPF (1) increases as the velocity of air over the coil increases; (2) decreases as the pitch of the fin decreases and (3) decreases as the number of rows of the coil increases.

AIR MIXTURES

The mixing of air streams can take place when :-

The fresh air drawn into air handling unit is mixed with re-circulated room air prior to conditioning and supply into the building.
Supply air is blown through supply grilles or diffusers into the room.
Exhaust air is discharged from the building into the external atmosphere.
The discharge air from an external dry or evaporative cooling tower is released into the atmosphere.
Steam from cooking equipment is released.
Opening doors between rooms connects areas held at different temperature, humidity or pressure states.
Air is extracted from different rooms and is mixed in the recirculation ductwork.
Air from different parts of the same room is drawn towards the extract grill and into ductwork.

Whenever such a mixing process take place, changes occur in the air condition. In comfort air conditioning, room air extracted into the return-air duct may or may not accurately represent the room-air condition around the occupants owing to the relative mixing of air from different parts of the room. It is important to summate mass flow rates for accurate results although an approximation can be made by adding volume flow rates. The inaccuracy here will be due to the changes in air density as the temperature change during the mixing process. The mixed air condition lies on a straight line connecting the two end states. Where,

Q₁= volume flow rates of fresh air (m³/s)

Q₂= volume flow rates of return-air (m³/s)

Q₃= volume flow rates of mixed air (m³/s)

An approximation to the mixed air temperature can be made from the volume flow rates and DB temperatures of the two streams, often with sufficient accuracy for plotting on the psychrometric chart, that is to within 0.5^oC DB, by making the assumption that the air densities and specific heat capacities remain practically constant. Divide each side by Q_3;

Where;

t₁= DB temperature of fresh air (m³/s)

t₂= DB temperature of return-air (m³/s)

t₃= DB temperature of mixed air (m³/s)

Anly Float Less Level Switch Rosak Atau Tidak

noreply@blogger.com (buildingservices) — Sun, 08 Feb 2009 17:03:00 +0000

Menentukan sama ada Anly Float Less Level Switch Rosak Atau Tidak?

1. Keadaan Rosak				2. Keadaan Baik


6	5	4	3	6	5	4	3
Floatless Level Switch				Floatless Level Switch


7	8	1	2	7	8	1	2

* kesan kerosakan				* untuk keadaan normal
menunjukkan terminal				terminal 8 dan 1 tiada
8 dan 1 akan ada				bekalan elektrik
bekalan elektrik				(louping) dan
(louping).				indicator light bagi PB OFF
				akan berfungsi.

* Pastikan terminal 5 (Live) dan terminal 6 (Neutral)
dipasang sebagai input voltage.

Faktor-Faktor Kejuruteraan Didalam Sistem Bekalan Air

noreply@blogger.com (buildingservices) — Sun, 08 Feb 2009 16:37:00 +0000

Faktor-Faktor Kejuruteraan Didalam Sistem Bekalan Air

1. Kala rekabentuk
- tempoh 5 tahun, 10 tahun dan sebagainya.
2. Jumlah Permintaan
- kegunaan domestik dan pertanian.
3. Tahap dan Keberkesanan Perkhidmatan
- kuantiti air yang dapat banyak permintaan.
- kualiti air yang dibekalkan.
4. Mengenal Pasti Sumber Air Mentah
5. Kemampuan
- mengolah dan membekalkan.
- dari segi penyimpanan, pemprosesan dan rawatan.

Kirakan Keamatan Lar, (I)

noreply@blogger.com (buildingservices) — Sun, 08 Feb 2009 15:21:00 +0000

Diberi Illuminance Pencahayaan, E bersamaan 100 Lux untuk kes diatas ini, kirakan keamatan Lar, I dalam unit cd (Candelar) serta buktikan samada 100 Lux bagi nilai E adalah tepat?

Penyelesaian:

Formulanya ialah

Data yang diberi ;

E = 100 Lux

d = panjang keamatan (Luminius Intensity)

= 3 meter

d x d = 9 meter

maka;

= sudut pada satah (permulaan) iaitu 0 darjah

= cos 0

= 1

100 Lux = (I x 1)/9

I = 900 cd

maka, keamatan lar bagi punca cahaya ini ialah 900 cd.

Pembuktian:

E = (900 x 1)/(9)

= 100 Lux (Terbukti)

Peranan Cahaya Siang

noreply@blogger.com (buildingservices) — Sun, 08 Feb 2009 15:10:00 +0000

- boleh diperolehi daripada bukaan tingkap.
- berfungsi untuk mendapatkan hiasan yang lebih menarik dalam sesebuah bangunan.
- ia menghasilkan "visual contact".
- ia juga boleh menjimatkan penggunaan elektrik.

Quotation 1205

noreply@blogger.com (buildingservices) — Sat, 07 Feb 2009 17:27:00 +0000



		BUILDING SERVICES WORLD ENTERPRISE (PGH 78319576-E)
		QE 205 POLITEKNIK TUANKU SULTANAH BAHIYAH
		09000 KHTP KULIM KEDAH
		TEL : 019-4745731
		www.buildingservicesworld.blogspot.com


Kepada : ________________________________			Tarikh :	8/2/2009
Lokasi : N0 1205/Lrg 28/2/Bandar Sri Mahkota

Bil	Lokasi	Keterangan	Kuantiti	Harga (RM)
1	Porch Area	Pemasangan Lampu Pendaflour 40W	1	3
2	Main Entrance	Pemasangan Lampu Pendaflour 40W	1	3
3	Room No 1	Pemasangan Lampu Pendaflour 40W	1	4.5
4	Room No 2	Pemasangan Lampu Pendaflour 40W	1	3
5	Room No 3	Pemasangan Lampu Pendaflour 40W	1	3
6	Kitchen Area	Pemasangan Lampu Pendaflour 40W	1	3
7	Toilet	Pemasangan Lampu Pendaflour 20W	1	3
8		Aksesori	L/S	21.5
Jumlah Keseluruhan				44

DISEDIAKAN : ___________________			DI TERIMA:	___________________


		*IBU PEJABAT : FAMSY ENTERPRISE (PGG 25943936-A)*
		*IBU PEJABAT : FAMSY ENTERPRISE (PGG 25943936-A)*

COMFORT AND PSYCHROMETRICS

noreply@blogger.com (buildingservices) — Thu, 05 Feb 2009 16:19:00 +0000

COMFORT AND PSYCHROMETRICS

General Objective

To understand the psychrometric processes of heating, cooling, humidification and dehumidification.

INTRODUCTION

The air that surrounds us has to be maintained at the correct conditions for us to be comfortable. The air in our homes is treated by the processes of heating, cooling, dehumidifying, humidifying, and cleaning it so that our bodies will give off the correct amount of heat for comfort.

THERMAL COMFORT

Certain combinations of air temperature, relative humidity, air movement and mean radiant temperature (MRT) will result in what most people consider thermal comfort. When these combinations are plotted in a psychrometric chart, they define an area as the comfort zone. This chart also indicates the type of discomfort one experiences outside of the comfort zone. The comfort zone should be the goal of the thermal design of a building because it defines those conditions that most people in our society find comfortable.

PSYCHROMETRICS

The study of air and its properties is called psychrometrics. When we move through a room, we are not aware of the air inside the room, but the air has weight and occupies space like water in swimming pool. Air weights 0.075 lb/ft³at standard atmospheric conditions and the density of water is 62.4 lb/ft³ . Air like water, offers resistance to movement. For example invert an empty glass and push it down in water. The air in the glass resists the water going up into the glass. Cooling, heating, humidifying, dehumidifying and cleaning out air describes the air conditioning profession. Air consists of approximately 78% nitrogen, 21% oxygen and 1% other gasses. Water in the form of lower-pressure vapor is suspended in the air and called humidity.

HUMIDITY

The moisture content in air (humidity) is measured by weight, expressed in pounds or grains (7000gr/lb). Relative humidity is the most practical and most used for field measurements. It is based on the weight of water vapor in a pound of air compared to the weight of water vapor that a pound of air could hold if it were 100% saturated.

DRY BULB AND WET BULB TEMPERATURES

The moisture content of air can be checked by using a combination of dry-bulb (DB) and wet-bulb (WB) temperatures. DB temperature is the sensible-heat level of air and is taken with an ordinary thermometer. WB temperature is taken with a thermometer with a wick on the end that is soaked with distilled water. The reading from a WB thermometer takes into account the moisture content of the

air. It reflects the total heat content of air. Note that a 100 % relative humidity, DB and WB are equal.

DEW POINT TEMPERATURE (DP)

The dew-point temperature is the temperature at which moisture begins to condense out of the air. For example, if you were to set a glass of warm water in a room with temperature of 75^oF and 50% RH, the water in the glass would evaporate slowly to the room. If you gradually cool the glass with ice, when the glass surface temperature becomes 55.5^oF, water will begin to form on the surface of the glass. This temperature at which water forms is called the dew point temperature of the air. Air can be dehumidified by passing it over a surface that is below the dew point temperature of the air, moisture will collect on the cold surface for example, an air conditioning coil. The condensed moisture is drained and this is the moisture that we see running out of the condensate line of an air conditioner.

ENTHALPY

Enthalpy is the total heat contained in lb of a substance. It is measured from a reference (datum) point. This reference point is 0^oF (-17.8^oC) for dry air, 32^oF (0^oC) for water vapor and –40^oF (-40^oC) for refrigerants. A psychrometric chart in metric units uses 0^oC as a reference base.

PSYCHROMETRIC PROCESS

The following examples show how different processes of air conditioning are plotted.

Air is heated. Movement through the heating equipment can be followed as a sensible-heat direction on the chart
Air is cooled. There is no moisture. This shows a sensible-heat direction on the chart.
Air is humidified. No heat is added or removed. An increase in moisture content and dew point temperature shows
Air is dehumidified. No heat is added or removed. A decrease in moisture content and dew point temperature shows
Air is cooled and humidified using an evaporative cooler.
Air is heated and humidified is the most common in the winter application. This will show both a rise in temperature and an increase in moisture and dew point temperature .
Air is cooled and dehumidified is the most common in the summer application. A decrease in temperature, moisture content and dew point temperature will occur
It is important to notice that any change in heat content or moisture content of air will cause a change in the wet bulb reading and therefore, a change in the total heat content.