National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, April 7, 2021

Question:

I've been a subscriber to the CQD for years. Plenty of great insight in the responses. I do understand the questions can only be answered at face value and the responses are based on the information provided. That said, my simple question is on the load side of a service disconnecting means can the neutrals and grounds be connected together in a subpanel? If not, what NEC rule prohibits this?

Thanks,

Greg Bernard

A

Answer:

Hello Greg, and thanks for the comments. This response takes care of multiple questions recently submitted on the same subject. On the load side of the service disconnecting means generally the neutrals (grounded conductors) and equipment grounding conductors in a panelboard need to be kept separated and insulated from each other. The reason is to not introduce neutral current on the equipment grounding conductor(s) and non-current-carrying parts of equipment. The NEC requirements in play here are 250.24(A)(5) and 250.142(B). The exceptions to 250.142(B) do not ally to this situation.

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