National Electrical Installation Standards

Standards as High as Your Own

Friday, October 27, 2023


Good morning, occasionally manufacturer’s installation instructions will contradict the requirements of the NEC®. I know that the manufacturer can require things above and beyond the requirements of the NEC®, but can the manufacturer installation instructions be less restrictive than the NEC® minimum? If so, what rules do we follow? Best, Rick


Hello Rick, great question. The manufacturer’s installation instructions are part of the listing of a that equipment or product, as such to maintain the listing of that equipment or product the instructions must be followed even if they are more restrictive than the NEC®. In the rare occurrence the installation instructions are less restrictive than the NEC®, then the more restrictive requirements of the NEC® would take precedence. While it does happen, it is not very common as most electrical equipment and product standards are written with the NEC® in mind. Also, the NRTL that evaluates the equipment or product will often require the manufacturer to address the conflict in the instructions before providing the listing approval. Occasionally, this will happen when a new edition of the NEC® comes out, and the instructions are not updated. However, it can also be an indication of a product that is not listed or is bearing a listing mark without authorization. When these situations arise, it is advisable to contact the manufacturer and/or NRTL that has listed the product so it can be investigated and resolved.  

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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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