National Electrical Installation Standards

Standards as High as Your Own

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  • February 18, 2020

    Greetings! Are junction boxes above a sheetrock ceiling considered accessible, if you must remove a 2 X 4 lay-in light fixture to access the box? Kelvin Brown
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  • February 17, 2020

    Hello, regarding smoke detectors and fire dampers on ducts. I have always connected them and seen them connected with FMC or BX cable because the duct could move or is not rigid, so I am looking for clarification. I was reading the IBC recently and came across "909.12.2 Wiring". In addition to meeting requirements of NFPA 70, all wiring, regardless of voltage, shall be fully enclosed within continuous raceways. The commentary reads "Wiring is required to be placed within continuous raceways, which provides an additional level of reliability for the system. The definition of the term “raceway” in NFPA 70 lists several acceptable types of complying raceway that can be used; however, manufactured cable assemblies such as metal-clad cable (Type MC) or armored cable (Type AC) are not included". No one has said anything to me before, but you know how it goes, you don’t know until someone opens a can of worms... Camilo Rodriguez
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  • February 14, 2020

    NECA Team, are isolated ground rec receptacles and circuits permitted to be installed in patient care locations of health care facilities? An engineering firm we are working with says we can't install them in these locations. We were hoping you could provide some Code-based clarification? Thanks for this online NEC service. We are on the 2017 NEC. Monica Hill
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  • February 13, 2020

    The Code Question Of The Day for Friday, December 20, 2013 has the exactly wrong/opposite statement for what is actually code. The sentence "The conductor insulation should have a dielectric constant not less than 3.5..." should instead read "The conductor insulation should have a dielectric constant less than 3.5..." ie. the word "NOT" should be removed. Cheers, R
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  • February 12, 2020

    Can I install 120-volt circuits in the same conduit with 480-volt circuits? Mark Hamer
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  • February 11, 2020

    Great work I love waking up and reading this forum every day! My question relates to arc fault circuit protection and when, if ever, it is acceptable to put a standard breaker back in on a circuit that tripped the arc fault breaker. I have been debating with several other electricians over this and I take the position that once an arc fault circuit breaker is installed, that circuit must remain arc fault protected. If it then trips The arc fault breaker, signaling a problem, that circuit must be repaired and continue to be arc fault protected. It is not allowed to simply put a standard, non arc fault breaker back in. To do that would be removing the safety device from the circuit and would be putting property and people at risk. If this is the case, where in the code book can this be found? Thank you. Be well. Michael
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  • February 10, 2020

    I'm using the 2017 version of the NEC. When installing nonmetallic sheathed cable in EMT for mechanical protection must I remove the outer jacket? Peter Izzo
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  • February 7, 2020

    We are having an argument about duplex receptacles and we are hoping you can clarify. Is a duplex receptacle one or two receptacles. It mounts in a single-gang box. Please provide any applicable Code reference. Thanks, Scott Anton
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  • February 6, 2020

    Can sheet metal screws be used to connect grounds to the metal of a fluorescent light fixture? We've been doing this for years, but an inspector has called us on it. Is there a rule? Chris Owen
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  • February 5, 2020

    Can a upper cabinet with a shelf intended for a microwave be fed from a kitchen small appliance branch circuit? Brian H&R Electric
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  • February 4, 2020

    Hello, I am a home inspector here in San Diego County. I did a home inspection and the A/C unit did not have an emergency disconnect. The electrical panel with the circuit breaker for the A/C was about 5 feet next to the unit. Question: Would an emergency disconnect be required to be installed if the circuit breaker for the A/C is in sight? Thank you, Ken Stoermer
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  • February 3, 2020

    A service entrance utilizes PVC conduit but there are two 90's and metal rather than PVC 90's are used. In many installations this is used to prevent the scoring of the inside of the PVC conduit as the wire passes through the bends. What conditions must be met to allow the use of the metal 90's in a PVC service entrance? Be sure and include your code book sections to backup your answer!
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  • January 31, 2020

    What size grounding electrode conductor is needed for a 200-ampere service if the service phase conductors are 250 kcmil aluminum? There is only one grounding electrode which is the Ufer ground. Adam Ford
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  • January 30, 2020

    Hi Charlie and Company, You folks do a great job with this forum, thanks! I'm working in an industrial facility and in one of the machine rooms there is an installation of 1-inch EMT containing both control conductors and small pneumatic copper lines for equipment. Is there any Code rule that prohibits installing equipment other than wires in electrical conduit? Any help would be appreciated. - Russell Knox
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  • January 29, 2020

    Are transfer switches installed in emergency systems required to be listed? Jim D.
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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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