National Electrical Installation Standards

Standards as High as Your Own

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Tuesday, March 27, 2018

Question:

Do equipment grounds need to be larger than the individual ungrounded conductors in parallel installations if the overcurrent device is large enough to require a larger equipment ground? Another words, does the “in no case needs to be larger” statement in 250.122 refer to the individual ungrounded conductors or the total circular mill of the entire ungrounded conductors of each phase?

Thanks; Mike

A

Answer:

Hey Mike thanks for your question. Yes. Equipment grounding conductors are sized based on the overcurrent device as stated in 250.122(F). Conductors are allowed to be connected in parallel if they meet all the conditions in 310.10(H). That concept uses multiple current paths to equally share the total current for each phase or grounded conductor. The circuit conductors supplying the equipment is the total area of all the "individual conductors" that are connected in parallel.

Equipment grounding conductors, for a parallel arrangement, might need to be larger than any one of the individual ungrounded conductors but does not need to be larger than all of the ungrounded conductors (total of the multiple paths) of any one phase.

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