National Electrical Installation Standards

Standards as High as Your Own

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Monday, July 16, 2018

Question:

Good morning to all of you, my name it's Eduardo M. I have a question regarding table 250.122, minimum size equipment grounding conductor, on the column of rating or settings in amperes  30,40,50,70,80, and so on it's missing the size. My question it's for an example what size would be on awg if I use for, 30,40, and 50 amperes, can you explain, thanks and I appreciate your patience.

Eduardo Morales

A

Answer:

Hey Eduardo thanks for your question. The last words in the heading of the first column in Table 250.122 are "Not Exceeding". For overcurrent device ratings or settings of 30, 40 or 50 amperes, those values exceed the 20 value in the first column so you have to go up to the 60 value resulting in a 10 AWG copper or 8 AWG aluminum conductor. The 10 AWG copper or 8 AWG aluminum would be the minimum size allowed for anything above 20 amperes up to 60 amperes. A change to remove some of those intermediate values was made in the 2011 NEC.

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