National Electrical Installation Standards

Standards as High as Your Own

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  • August 8, 2019

    1. Is NM cable allowed to pass through a hole in drywall (without a box) and terminate directly to a disposer? 2. Is NM cable required to be protected under a sink? Keep up the good work. This is one of the few sources that is solidly grounded. Elijah J
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  • August 7, 2019

    This question is about a single-family dwelling that has a 200-amp new panel with a 100 amp sub panel, the subpanel feeds all the branch circuits, and some of the branch circuits have an old two wire Romex 2 hots 1 bare ground for the oven and dryer and one hot one neutral for the other branch circuits, the city wants all the 220 volt Branch circuits to go all the way back to the main panel where it is bonded does this sound like a good correction?Victor Gonzales
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  • August 6, 2019

    Re: CQD answer published July 12 & 29, 2019 -480 V 3 wire needs 277 V-3 Charlie, I have not seen any discussion about deriving a neutral by installing a zig-zag transformer. They come many sizes. Just passing this on.Bill Petrovic | Design Engineer
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  • August 5, 2019

    Can you use 12ga thhn stranded wire in EMT conduit coming from a 20 amp breaker that feeds a few outlets and flood lights (led)? What are the spacing dimensions required to secure conduit? I was getting bids to run another 220v circuit into the laundry room and was wondering why you couldn't run two 220v outlets from one breaker? I'm not an electrician but I've come across a few questionable things licensed electricians have done so to make me feel better I like to understand the logic behind the installation.Thanks, Justin
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  • August 2, 2019

    Table 300.5 states minimum cover of 24" is required for raceways listed for direct burial without concrete encasement for "streets... and parking lots." What is the minimum cover if with concrete encasement? Don Jeppson
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  • August 1, 2019

    I went on a call about a residential kitchen gas/convention oven unit (12.2 amps) tripping a 15 amp breaker. The 120v oven cord passed through the floor into the cellar and was plugged into a non-dedicated circuit receptacle mounted to a joist. So I have a couple of questions. 1. Can the cord pass through the floor and plug into the receptacle like that? 2. If I run a new 120v 20 amp receptacle up behind the stove does it have to be GFCI protected if it's within 6 feet of the kitchen sink, yet hidden behind the stove? 3. Can the receptacle be behind the stove or would it have to go in an adjacent cabinet for easy access like with a dishwasher?Thank you. Richard Cressotti
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  • July 31, 2019

    Are barriers needed in a switchboard to separate the fused and non fused conductors? My feeling is that the gutter space in a switchboard is not raceway and not subject to the NEC code 230.7 article 100.Patrick Farkas
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  • July 30, 2019

    If our UPS (batteries integral to equipment ) rated VA is 750VA/ 1000VA and the when main power is disconnected, the back-up time is not more than five minutes, we want to know if the EPO (Emergency Power Off) device is necessary or not?Sammi Lee
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  • July 29, 2019

    What happen to Monday's answer? Jimmy; Question of the day has no answer. Patrick Cook The answer to Monday July 22nd question was not published on Tuesday so we are repeating it here. What is the length of run in a 2" PVC Conduit before it needs an expansion coupling?Glenn Masters
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  • July 26, 2019

    Re: CQD answer published Friday, July 12, 2019 -480 V 3 wire needs 277 V-2 Sirs: As always, thank you for your valuable service. It is appreciated by many. Regarding 'converting' 3 phase 480 volt to lighting poles to 1 phase and deriving a neutral. Would it be legal and code-compliant to disconnect one phase at the breaker; re-identify it as a neutral; change the 3-pole breaker to a 2-pole single phase breaker; and obtain your neutral in that fashion? With so many conversions of parking lot lights to LED, there is often as much as a 75% reduction in load and many of the lights are 277v instead of the old 480v. The old systems didn't need a neutral; with 277v lighting this would seem to be the easiest conversion. Is it allowable? Thank you, Gary
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  • July 25, 2019

    Re: CQD answer published Friday, July 12, 2019 -480 V 3 wire needs 277 V-1 Good Morning, You should also have cautioned Mr. Greb that simply driving a ground rod will not create a low impedance path back to the source to trip the breaker or blow the fuse. Mr. Greb would be creating an extremely unsafe condition, by not having a properly sized equipment grounding conductor.Thanks, Carl
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  • July 24, 2019

    Can metal wiremold be installed under flooring surfaces. Allen de Steiguer
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  • July 23, 2019

    I read code question of the day just about every day. Thanks for this service. I am about assemble light fixtures in a lighting showroom. I will have to install and wire many fixtures. Because these fixtures are for sale and may be removed for new products can this installation be considered temporary? I don't think so because many fixtures will be installed for months or even years. But is their some kind of special provision for relaxation in the NEC for this type of situation? I've looked through Article 590 and I see time constraints. I would like to hear your opinion.Thanks Dave
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  • July 22, 2019

    What is the length of run in a 2" PVC Conduit before it needs an expansion coupling?Glenn Masters
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  • July 19, 2019

    Hello all, I have a new storage building at a local high school being fed from an existing panel in the school. The engineer had me pull a grounding conductor in with the feeders, but my inspector is saying I need to bond my neutral at the disconnect for the new building.... my take is that the neutral is already bonded at the main switchgear for the school and bonding the neutral again would cause the grounding conductor to be a parallel run with the neutral back to the panel the building is fed from (not the switchgear). For this on whether or not the neutral should be bonded at the new building and if so, should I eliminate the ground I pulled in with the feeders... Fyi the service is 225A 480/277V 3 phase 4 wire, not that that should change anything. Thank you,Jeremy Buxman
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ABOUT CQD: The Code Question of the Day (CQD) is NECA and ELECTRICAL CONTRACTOR Magazine’s flagship National Electrical Code (NEC®) public forum for the industry, sponsored by EATON. The daily distribution of Q&A generates a lively dialogue and shares relative Code-based practical responses.

SUBMIT YOUR CODE QUESTION: Click here to submit a question to for inclusion in an upcoming edition of the Code Question of the Day, or email

CHARLIE TROUT: 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. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

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IMPORTANT NOTICE: Unless the question requests a response based on a specific edition, all answers are based on the latest edition of NFPA 70® National Electrical Code®.

This correspondence is not a formal interpretation of the NEC® and any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, the NEC Correlating Committee any Code-making panel or other electrical technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services. 

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