National Electrical Installation Standards

Standards as High as Your Own

The National Electrical Code is the bedrock of the electrical construction business.

Do you know all the ins and outs of the Code? NECA and Electrical Contractor magazine are pleased to present their daily online feature, “Code Question of the Day.”

  • ?
    Friday, February 23, 2018


    Article 501, 501.15 C 6 states that the conductor or optical fill, the cross section area of seal shall not exceed 25% of the cross section area of a ridged conduit of same trade size?? is this for pouring in chico into EYS, don't understand this, conduit fill vs. seal off fill when its the same conduit?????

    Mike Garcia

  • ?
    Thursday, February 22, 2018


    Good Morning, How do we enforce 210.12(A)(4)d. I’ve called device manufacturers and they say UL hasn’t established a test for “system combination type AFCI? They imply it up to the inspector to accept or deny.

    Thank you, Ed Sim



    Hey Ed thanks for your question. I believe you are correct that system combination type AFCI's are not available. If that is the case then that option cannot be used and one of the other methods in 210.12(A) must be used. Sometimes rules are included in the NEC for products that are not yet available but that allows manufacturers to develop them if they think there is a market.

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.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. Visit for more information. NEISÔ can be purchased in three formats: as paper books, on CD, or as electronic downloads.

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