National Electrical Installation Standards

Standards as High as Your Own

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  • July 17, 2020

    Hope everyone is staying healthy during this COVID-19 pandemic. My question is simple, can an emergency circuit junction box be identified by magic marker with just the letters "EM" written on the box cover? We have inspectors that require the word "Emergency."Mike Riley
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  • July 16, 2020

    Hello CQD, What rules in the NEC address derating of wire (conductor) ampacity? Thanks,Sonny Lynch
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  • July 15, 2020

    Hello and thanks for this Code service. I have an inspector that is requiring my new home generator and transfer equipment to transfer to generator power within 10 seconds. Is this an electrical Code requirement?Peter Turner
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  • July 14, 2020

    Hello, I have a question; I have an electrical breaker box in my kitchen. Covered with a cabinet door is that acceptable?Sandra Nelson
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  • July 13, 2020

    Greetings CQD, Thanks for this service. Can the appliance end of the 12-2 nonmetallic sheathed cable fed from a separate 20-amp circuit be hard (directly) wired to a 20-amp female attachment plug or does the appliance require a single gang box and grounded outlet? Steve Saccoccio
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  • July 10, 2020

    Hi Die Hard Code Fans, I'm interested if there are NEC requirements that address accessibility and ADA requirements. Any help would be appreciated. Charles Lamm
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  • July 9, 2020

    Comment on CQD for Friday May 22, 2020: Hi Code Question of the Day, Oh yes, the constant battle of installing a receptacle with the ground up or down. Two comments, first working in southern Michigan and working with electricians from Ohio, they always installed them with the ground up and the electricians from Michigan usually installed them with the ground down. Must be something about buckeys! Second, I've noticed in medical facilities ( doctor and dentist offices) the ground is installed up. I think that is due to the cord configuration on the equipment that is plugged in. Flat cord caps that would have the cord go up before dropping back down to the floor and straining the cord. Just my two-cents on the question that will never be solved to everyone's satisfaction. Gary Lazette
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  • July 8, 2020

    Hello Code Friends, What is the standard (or is there one) for selecting proper lug barrel size for a given AWG wire size? Scott Alsop
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  • July 7, 2020

    Hello CQD, I want to thank you for the great service you provide to the electrical industry. I’m sure it’s challenging trying to answer code questions others will critique. In your response to the Code Question from Wednesday May 20th, one could add that the requirements of 300.4(D) would apply as well. I believe 300.4 lays out the exact scenario that Scott is dealing with. Thanks again for all your hard work! Trevor Turek
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  • July 6, 2020

    Comment on CQD Question and Response for May 20, 2020: Hello, Regarding the question and answer for using FMC behind a furred out sheetrock wall posted on Wednesday 05/20/20, it should be noted that 348.20(A) states the minimum trade size for FMC allowed is 1/2". The OD of 1/2" FMC is roughly 7/8 and furring strips are only 3/4" leaving the FMC an 1/8" larger than the hollow wall space. For that reason MC cable is preferred over FMC since the OD of MC is only 3/8". Also noteworthy is 300.4(D) which comes into play should the FMC or MC be run next to a furring strip. The 300.4(D) Cables and Raceways Parallel to Framing Members and Furring Strips. In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed parallel to framing members, such as joists, rafters, or studs, or is installed parallel to furring strips, the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 32 mm (11⁄4 in.) from the nearest edge of the framing member or furring strips where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.6 mm (1⁄16 in.) thick. Exception No. 1: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing. Exception No. 2: For concealed work in finished buildings, or finished panels for prefabricated buildings where such supporting is impracticable, it shall be permissible to fish the cables between access points. Exception No. 3: A listed and marked steel plate less than 1.6 mm (1⁄16 in.) thick that provides equal or better protection against nail or screw penetration shall be permitted. Richard Cressotti
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  • July 3, 2020

    Hello Electrical Team, Where does the NEC say I have to test my wiring for insulation integrity before energizing circuits? Harold Furman
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  • July 2, 2020

    Hello and hope everyone is doing well during this COVID-19 pandemic. I recently installed an underground circuit in my front yard and used schedule 40 PVC sprinkler pipe. The inspector turn the installation down saying that I cant use sprinkler pipe for electrical wiring. Is there a Code rule that prohibits this? Any help would be much appreciated. Thanks, Bruce Compton
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  • July 1, 2020

    Hi Code Question of the Day, What are the wiring requirements on wiring of a mechanics shop, can they be wired using nonmetallic sheathed cable where the wiring is covered in NEC Chapter 3? William Martell
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  • June 30, 2020

    Hello, Section 110.12 requires electrical equipment be installed in a neat and workmanlike manner. Can anyone explain what that means, because the NEC seems to fall short of describing this. I think workmanship is in the eyes of the beholder. Daniel Simpson
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  • June 29, 2020

    Re: Code Question of the Day for May 14 Greetings Code Friends, Question: My question is if I have a metal outlet box and equipment grounding conductors in the box, do I have to connect the EGC to the box using a listed green grounding screw? Answer: Hi Mel, Thanks for participating. No, the connection to the metal box should be made using one of the methods provided in 250.8. If a screw is used to accomplish this connection, it should be in accordance with 250.8(5) and be a machine screw that engages not less than two threads or is secured by a nut. No requirements for such screws to be green or listed. If the connection is made with a grounding clip (pressure connector), the clip would have to be listed. Comment: I think I know why some think that an Equipment Grounding Conductor screw must be required to be listed. I taught electrical wiring in a Vo-Tech High School for 28 years. About 15 years ago there was a textbook that stated the EGC had to be connected to metal boxes with a green listed grounding device or screw. That made it seem that the screw had to be listed and green. The actual wording in the 2002 NEC that the text book was based on said “by means of a grounding screw that shall be used for no other purpose or a listed grounding device.” (250.148(B)). It said nothing about the screw having to be listed or green. The list of permitted methods in today’s 250.8(A) did not appear until 2008. I am sure many of today’s electricians probably were exposed to that book. Before a lot of people write in saying that the screw must engage at least two threads, all 10-32 screws have 32 threads per inch, no matter what color they are or who made them. Bob Morin
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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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