National Electrical Installation Standards

Standards as High as Your Own


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.

  • ?
    Monday, December 4, 2023


    Good morning code enthusiasts, Where cable tray is covered with solid unventilated covers, Section 392.80(A)(1)(b) say that the Ampacity of Multi-Conductor Cables in Cable Trays shall be derated to 95%. The contractor wants to use this type of unventilated cover but make it larger than the tray to allow airflow over the cables, and not use the 95% derating factor.

    Would this be acceptable? I don't see anything in the code allowing the cover to be oversized to avoid the derating factor. If anything, I think this could possibly be a UL listing issue, but the code doesn't seem to permit this. Best. Clive T.
  • ?
    Friday, December 1, 2023


    Hi Charlie, I can't start my day without checking in on the Code Question of the Day. My question is clarification for the routing of Service Entrance conductors. Specifically, when a whole house transfer switch is installed, which also serves as the service disconnect. I have seen the service conductors routed through the existing panel and then through a short piece of PVC to the new service disconnect/transfer switch. Then a separate PVC is used to bring the main power feeder back to the existing panel and connect to the main feeder breaker to supply what will now be the Sub-Panel for the entire house. Section 230.7 indicates that service conductors can't be installed in same "raceway" with other conductors but doesn't recognize the gutter area of a panel as a raceway (as explained in the enhanced content area in the NFPA link website).
    The installation described above doesn't seem to meet the intent of the code but the actual wording in the code may allow this. What say you, Charlie? Thank you again for your insight on these Code questions, much appreciated! Rick Kinsman


    Hello Rick, thanks for the kind words and participating in the CQD. This poses a great question as the to the intent of 230.7. In the traditional installation the gutter space would accommodate branch-circuit, feeder, and service conductors as they are all terminating in that enclosed panelboard. Since the service conductors are not terminating inside this enclosed panelboard, it could be argued that a violation of 230.7 now exists. Additionally, there may be a manufacturer installation instructions/listing issue as that enclosed panelboard may not be designed for pass though applications.

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.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. NEIS can be purchased in the NECA Store in three formats: a printed or  PDF download of a standard or, as an  annual subscription service.

NECA SAFETY PRODUCTS & PUBLICATIONS: NECA produces electrical safety publications and products for the industry including jobsite safety guides, handbooks and resource kits. View a full listing of available resources and products »

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. 

UPDATE YOUR SUBSCRIPTION PREFERENCES: Subscribe or Unsubscribe from this list.