National Electrical Installation Standards

Standards as High as Your Own

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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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  • January 28, 2020

    Is a feeder conduit permitted to pass through an exit stairwell enclosure? The lighting in the exit stairwell is supplied by the emergency system (generator) supplying the building. Any guidance would be appreciated, Sammy Duncan
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  • January 27, 2020

    Can I install a 208Y/120-volt circuit in the same conduit as a 480Y277-volt circuit? Slim Jim
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  • January 24, 2020

    If I install 2 AWG copper conductors in a run of 2-inch EMT, are plastic bushings required in all enclosures that the circuit is installed to? An inspector is requiring I install them but I can't find a rule in the NEC? The EMT fittings (connectors) I used have plastic throats (integral with the connectors) at the threaded ends. Any help would be appreciated. Carl Davis **NOTE: Correction to yesterday's answer (1-22-2020): "The 2020 NEC not now directly prohibits this orientation. See Section 408.43."
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  • January 1, 0001

    In a new house construction project, can the electrical panel be in a floored attic if the installation meets all minimum set backs, and has access by pull down stairs? What code sections would apply? Eileen Felton
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  • January 20, 2020

    What is the maximum voltage drop for any branch circuit installed in a sensitive electronic equipment panel board? -Timothy Hardt
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  • January 21, 2020

    Is THWN conductor insulation suitable for use for the branch circuits for an operating room that is supplied by an isolated power system? Anthony Goode
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  • January 23, 2020

    Thank you for providing this service! I have an ungrounded three-phase 480-volt delta system and was wondering what the phase-to-ground voltage is. Hopefully you can provide some clarification. Not sure if the NEC addresses this situation. Kenneth McQuaid
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  • January 22, 2020

    Can a panelboard be installed on its back in the face up position? The NEC does not seem to address this orientation. Any guidance would be very appreciated. Thomas Dye
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  • January 17, 2020

    Gentlemen, I’m hoping you can help with an opinion. As you seem to understand how to apply the NEC rules from a practical viewpoint. Section 230.72 indicates the two to six service disconnects permitted in Section 230.71 must be grouped. There is no maximum distance on between the two to six disconnects, so how far is too far before the installation would not meet the grouping requirement. Could signage be installed to assist in meeting the grouping requirement? Any opinions would be very appreciated. Mark Taylor
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  • January 16, 2020

    Can electrical metallic tubing (EMT) be installed to supply a fire pump. The installation would be from the load side of the fire pump controller overhead on a ceiling of the fire pump room and then a vertical drop of the ceiling to the motor. There would be a transition from EMT to liquid-tight flexible metal conduit within 2 feet of the motor terminal housing. Job specifications are calling for rigid metal conduit. Thanks for any Code view on this, Mike Long
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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 codequestion@necanet.org

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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