National Electrical Installation Standards

Standards as High as Your Own

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  • May 15, 2017

    We have a custodian that leaves the door to the electrical room open. The electrical room is in the teachers' lounge/ copy room. We have told him to keep it shut. Is there a certain code that says that door should be shut? If so, could you reference the # so I can show him. Thanks Doug Gerke
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  • May 12, 2017

    Thank you in advance. 300.15(F). A “go-from” (transition or combination coupling) when being used for a cable to conduit, example; MC to EMT. Would this be considered a pull point that would require the fitting to be accessible? Personally, I do not believe it is a pull point but I have been wrong before Thank you, Jim Dorsey
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  • May 11, 2017

    What size ground rod and how many do I need for a 1200amp 480volt three phase service. I have a 3/0 wire. Patrick Rosenauer
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  • May 10, 2017

    Re: CQD answer published Tuesday, May 2, 2017 -Transfer Equipment Health Care Paragraph 517.26 states “the life safety branch of the essential electrical system shall meet the requirements of Article 700, except as amended by Article 517”. NFPA 99 also has qualifying statements that refer back to complying with NFPA 101 and NFPA 70-Article 700 (NFPA 99-2012;, In our office we have always considered that Life Safety Branch and Critical Branch need to comply with NFPA 70-700 and NFPA 7-701, except as amended by NFPA 70-517. Edward M. Grafe
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  • May 9, 2017

    Hello Charlie, There is a situation that my Electrical Supervisor and crew found where a metal clad cable was installed in a 4" PVC conduit run, along with both 120/208V feeders and 277/480V lighting branch circuits. The reason the MC cable was installed, I believe, was to provide separation for an emergency circuit. Under 330.10, (A), (7) the NEC states MC cable can be installed in any raceway. Three and a half years after this installation was complete we experienced a short between the feeder conductors and the lighting branch circuit where the insulation was damaged. I believe the cause of the damage was pulling the MC cable in the conduit with the other conductors. My question is: Can you find anything in what I described that may be a code violation? Sincerely, Gary
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  • May 8, 2017

    Re: CQD answer published Monday, May 1, 2017 -Small Conductors and terminations Folks, The retention of the 60° C rating is entirely due to the design of overcurrent protective devices and other electrical equipment relying on the mass of conductor for heat dissipation. If you place too small a conductor on a breaker or fuse due to using the wrong temperature rating of the insulation the device will be operating at a higher temperature than designed and you will have nuisance tripping. Unfortunately this is never explained either by the code or instructors. A circuit breaker or fuse is typically sized based on the temperature rating of the insulation, not the conductor size. Per NFPA 70 110.14(C)(1)(a) & (b), all electrical equipment rated 100 amperes or less or marked for conductors #14 AWG through #1 AWG are designed for 60° C, unless otherwise marked by the manufacturer, while designs for over 100 amperes or marked for conductors larger than # 1 AWG are intended for 75° C, unless otherwise marked by the manufacturer. Currently there is no default for the 90° C conductor insulation range. Cordially, Bill Nolte
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  • May 5, 2017

    Hello, 2017 NEC Section 400.12 mentions power supply cords with flexible cables. What is the difference between the two? How does UL 62 & UL 817 factor in? Thank you, John Bayduss
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  • May 4, 2017

    Hi I've got a service feeder question. I'm doing a remodel of a commercial retail store. There is currently a 3 phase 120/208 400 amp service which is being replaced by a 500 amp service. The existing switchgear has a 4 inch conduit run to it with parallel feed conductors in it. The plans call for 2 - 2 1/2 inch conduits with 250 mcm feeders for the 500 amp service and new switchgear. I would much rather use the existing 4 inch conduit and pull the parallel feeders in that than spend the money and time installing new conduits. My question is can I parallel two sets of 250 mcm in the 4 inch conduit, or do I need to up the size to 300 mcm with a 1/0 ground because of derating factors to be code legal? Rob Frees
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  • May 3, 2017

    Hi, does a receptacle mounted at 60” AFF, behind a flat screen TV, but still within 72” of the edge of a sink, need to be GFI? I see an exception for refrigerators in kitchens, does a similar exception exist for the situation above? Thanks, Jeff Dow
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  • May 2, 2017

    My question: If an existing bathroom is non-compliant in a home. Is there a problem with it being as how it is existing? I understand that the problem is when there is a remodel project that requires electrical work on that bathroom or if the customer is having nuisance tripping and calls an electrician to repair the problem. Than it must be brought up to code compliance. The previous question does not indicate he is having a problem or remodeling. We have hundreds of non-compliant bathrooms in our town. Bill
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  • May 1, 2017

    Start each day with you guy’s…Thanks, it exercise’s the old brain. The new requirements in 700.5, 701.5 & 702.5 for Field labeling the Transfer Equipment with the short circuit current rating of the ATS. This I assume is done by checking either the Coordination study and or the SCCR of the Normal & Emergency breakers suppling the ATS. My Question is I see no requirement for this in 517… It seems to me this would be important for Transfer Equipment on the Essential Electrical System to be field labeled with this info also? Thanks, Kelly Wofford
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  • April 28, 2017

    Good Morning, What is the history behind the small conductor rules of 240.4(D), specifically (3) and (5) & (7). If equipment terminations are rated for 75 degrees C why are the conductors still limited to the 60 degree column? Pat Lyon
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  • April 27, 2017

    Is there a minimum ground clearance to the bottom of a NEMA 3R rated CT enclosure? Patrick Gianotto Jr
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  • April 26, 2017

    Hey Charlie thanks for answering your questions here and shedding some light on these issues. My question is considering g when building new construction all romex wiring must be passed in studs or in a cavity attic or shaft of some kind. Presumably to prevent a screw or what have you from penetrating them. My question is in regards to the strapping on walls for the jiprock. How is it legal to place wires in this void, right behind the jiprock, stapled to the surface of the studs between rows of strapping. Typically the zone where they fish wires when renovating J Sparx
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  • April 25, 2017

    Listing of NM (Romex) Charlie, got into a discussion with a mechanical contractor about running NM through sealtite to an AC disconnect or condensing unit. Told him that it's a wet location and not permitted. So he asks if he strips the NM jacket and uses proper connectors is it legal? What is the listing of the conductors once the NM jacket is removed? Inspector vs Mechanical Please omit my name
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ABOUT CQD: NECA’s Code Question of the Day (CQD) is a leading National Electrical Code® forum for NECA and the industry. The CQD generates a lively dialogue and relative practical and Code-based responses to an ever-increasing and interactive audience.

IMPORTANT NOTICE: All answers are based on the latest edition of the National Electrical Code®, unless the question requests a response based on a specific edition. This correspondence is not a formal interpretation of the NEC®. Any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, or any technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services.

ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

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