NEIS: Code Question of the Day

NEIS: Code Question for Thu, 23 May 2013

Thu, 23 May 2013 00:00:00 +0000

Charlie, Thanks for the Code information. Were are going through a renovation project and are installing a 225-kVA transformer that has a 480-volt, 3-phase primary and a 208Y/120-volt 3-phase, 4-wire secondary. What size overcurrent device do we need to install on the primary side to provide transformer protection? There is a difference of opinion about the correct size breaker necessary. Some say 300 others say 350 amperes is okay. Thank you for your help and opinion. Mitch Stafford Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

NEIS: Code Question for Wed, 22 May 2013

Dear Charlie, I n a commercial building, in a mechanical room, there is an HVAC duct directly over the space where a panelboard is to be installed. The bottom of the HVAC duct is 9'-2" above the finished floor. The HVAC duct is 'foreign' to the electrical installation and can't be relocated. The panelboard is 36" in height. The structural ceiling is 13' above the finished floor. If the panelboard is installed where it would be convenient to work on and operate - let's say with its center at 4'-6" above the floor - the duct will then be located in the six feet of dedicated equipment space required by NEC 110.26(F)(a). It has been suggested, however, that the panelboard be installed at a height of two inches above the floor. This will result in 6' of dedicated equipment space above the panelboard as required, but with a panelboard that is inconveniently located at one's feet and knees. It seems as if locating the panelboard so close to the floor, merely to ensure we meet the requirements for dedicated equipment space is 'cheating' and should be addressed via suitable code language. It seems to us, that we would much rather have the panelboard located at a suitable and serviceable height, and forgo the 6' of dedicated equipment space in this particular situation. Are there any prohibitions in the NEC in regards to locating a panelboard at such a height? Are there any exceptions that would allow the panelboard to be located higher, and forgo some of the required equipment space? Best regards, Robert Moleti, P.E. Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Answer:

Hi Robert, Thanks for participating in the CQD. This is a good question and it comes up often. The short answer is no, the Code does not provide any exception to allow what is suggested in this design for the panelboard installation. The dedicated space is necessary for electrical equipment installation for the present and future installations of wiring to the panelboard. The other reason is to eliminate or minimize the possibilities of foreign contaminants to cause a damaging effect on the equipment. The NEC does not specify a minimum height for the operating handles of switches or circuit breakers in a panelboard from the floor but does address a maximum height of 6 foot 7 inches to the center grip of the switch or circuit breaker handle. If installing the panelboard creates a violation of the dedicated space requirements, or the maximum circuit breaker height requirements, the solutions are to relocate the duct or the panelboard to attain minimum compliance. Always check with the local authority having jurisdiction for their interpretation and how they will enforce these requirements of the NEC. Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Section: 110.26(E)(1), 404.8(A)

ANSWERS: Answers are the author's opinions and do not represent formal interpretations of the National Electrical Code.

All answers are based on the latest edition of the NEC, unless the question requests a response based on a specific edition.

CONTACT US: To submit a question, subscribe to Code Question of the Day, or remove yourself from this list, please send an e-mail to codequestion@necanet.org.

ABOUT THE AUTHOR: Charlie Trout is a nationally-known NEC expert and author. He served on three different National Electrical Code-Making Panels and is past chairman of CMP-12. He is also a member of the NECA Codes & Standards Committee. In 2006 Charlie Trout won the prestigious Coggeshall Award, given to recognize outstanding contributions to the electrical contracting industry in the technical and training area.

NECA STANDARDS & SAFETY PRODUCTS: NECA publishes the National Electrical Installation Standards (NEIS), a series of ANSI-approved performance and quality standards for electrical construction. Visit www.neca-neis.org for more information. NEIS can be purchased in three formats: as paper books, on CD, or as .PDF downloads.

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NEIS: Code Question for Wed, 22 May 2013

Wed, 22 May 2013 00:00:00 +0000

NEIS: Code Question for Tue, 21 May 2013

Dear Charlie, I'm following your Q/A site everyday. It's Great. I am learning and enjoying it a lot. I have a query. The size of the conductor buried underground as a grounding ring around a building is usually specified as AWG#2, or larger, with few ground rods as supplements attached to it as a ring. I wonder how do they calculate this size of ring conductor and how do they find the required number of ground rods attached to it. I will appreciate your feedback. Thanks in advance! Gul Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Answer:

Hey Gul, Thanks for the comments and thanks for participating. The minimum size required for a ground ring is 2 AWG copper. The list of permitted grounding electrodes is provided in Section 250.52(A). Ground rods are not required to be connected to the ground ring as the ground ring serves as the grounding electrode as provided in Section 250.52(A)(4). There fore, the NEC is silent on the minimum number of ground rods that can be connected to the ring. It is above the requirements in the NEC. The size of the grounding electrode conductor connected to a ground ring is as required by Section 250.66 and Table 250.66 except as permitted in 250.66(C). Section 250.66(C) indicates that the grounding electrode conductor that is the sole connection to the ground ring electrode, the grounding electrode conductor is not required to be larger than the size installed for the ground ring. Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Section: 250.52(A)(4), 250.53(F), 250.66, Table 250.66, and 250.66(C)

NEIS: Code Question for Tue, 21 May 2013

Tue, 21 May 2013 00:00:00 +0000

NEIS: Code Question for Mon, 20 May 2013

Hi Charlie, This is just a follow up comment on the Question and response for May 13, 2013. Multipole breakers must be used on solidly grounded systems and not on impedance grounded systems unless specifically rated. Most three-pole breakers are only suitable for solidly grounded systems. If the 2P application the 3P breaker is not solidly grounded, then it could be a problem. Nick Abbatiello Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Answer:

Hi Nick, Thanks for your great follow up and additional information. The breakers need to be used in accordance with how they are listed. The UL White Book also provides great information on the subject under Category DIVQ. Section 240.85 and the informational Note also provide information on the restrictions and proper application of circuit breakers. Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Section: 110.3(B), 240.85 and Informational Note

NEIS: Code Question for Mon, 20 May 2013

Mon, 20 May 2013 00:00:00 +0000

NEIS: Code Question for Fri, 17 May 2013

Charlie, I've been just reading the question of the day up until now. Here is my question. There is a new requirement to install a neutral at switch locations. The rule does not say one has to connect the neutral or use it. The issue is I can still purchase an occupancy sensor switch with a neutral pigtail and a switch that has only an equipment-grounding (green) conductor pigtail. Both are listed and available by more than one manufacturer. Is it a violation to install the switch without the neutral pigtail if both are listed and available when the NEC just requires the neutral to be installed in the switch location? Thanks for your time and wisdom. Peter Saunders Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Answer:

Hi Pete and thanks for participating. The NEC requires that where switches control lighting loads are supplied by a grounded general-purpose branch circuit, the grounded circuit conductor (neutral) for the controlled lighting circuit shall be provided at the switch location. The intent of this new requirement is that the neutral is required to be installed in that location so if a listed switch requires the neutral, it can be connected to the device. This keeps load current off the equipment-grounding conductor. The NEC does not currently require the connection of the installed neutral to that device, but perhaps it should. The listing of the product does. If there are two listed switches available on the market for installation that have a neutral and that do not, then it appears as thought the product standard needs to be revised. There is a restriction of load-side grounding connections located in 250.24(A)(5) and 250.30(A) that could also be used to require the correct switch to be used.

Section: 404.2(C), 110.3(B), 250.24(A)(5) and 250.30(A)

NEIS: Code Question for Fri, 17 May 2013

Fri, 17 May 2013 00:00:00 +0000

NEIS: Code Question for Thu, 16 May 2013

Hi Charlie, Great Code Forum here. My question is as follows: Are all junction and pull boxes required to be listed? Thanks in advance for your reply. Tim Hanson Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Answer:

Thanks for the nice comments and participation in the CQD. All junction and pull boxes are not required to be listed as a general rule, but some boxes are required to be listed such as boxes for luminaires (weighing more than 50 lbs.), boxes for ceiling-suspended paddle fans, and floor boxes. Part III of Article 314 provides construction specifications for boxes, conduit bodies, and fittings. Sometimes custom pull and junction boxes are necessary for unique construction features. This allows field fabrication of custom boxes to meet the special sizing requirements and shapes. Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Section: 314.27(A)(3), 314.27(B)
Source: Charlie Trout

NEIS: Code Question for Thu, 16 May 2013

Thu, 16 May 2013 00:00:00 +0000

NEIS: Code Question for Wed, 15 May 2013

Charlie, Thanks for the CQD. It is very informative. Here is my question. Is a separate disconnect switch required at a motor if the motor control center is within sight from the motor location? The blueprints indicate disconnects, but as I read the NEC, it is not a requirement. Your opinion would e greatly appreciated. Todd Creighton Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Answer:

Hi Todd. Thanks for the question. The disconnect in the motor control center can meet the requirements of the Code as long as it is within sight from the motor location. The term “In sight from” is defined in Article 100. Remember that in many areas, the plans and specifications are often more restrictive that the NEC minimums and become the requirements. Verify with the local AHJ and design or engineering firm responsible. Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}

Section: 430.102(B), 100 Definition of �Within Sight From�