National Electrical Installation Standards

Standards as High as Your Own

Friday, August 11, 2023


Hello Charlie and thank you for this wonderful service you provide! We work with refrigerated equipment, and we run into this issue quite often. When sealing conduits that pass thru a freezer wall, is silicone caulk an acceptable means to seal the inside of the conduit? Many jobs have it in the spec to use silicone but there are AHJs in our area that don’t accept this practice. We have had numerous issues over the years with using ‘perma-gum’ sealant and have found that silicone works the best.

Regards, Joe Frieders


Hi Joe, thanks for the kind words about the CQD. The requirements found in Section 300.7(A) specify that the sealant must be identified for use with cable insulation, conductor insulation, a bare conductor, a shield, or other components. The silcone being used will need to be identified for the use and the AHJ will need documentation from the manufacturer showing that the silicone is identified for the use. Sealants like polymer putty/caulk are often used as there are several commercially available versions specifically identified and listed for this purpose of sealing electrical raceways with conductors.

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.

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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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