National Electrical Installation Standards

Standards as High as Your Own

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Wednesday, March 6, 2019

Question:

240.4(B)(1): does this article restrict circuits with more than one receptacle outlet from using the next size breaker if the conductors are derated?

Barry Yeslow

A

Answer:

Hey Barry thanks for your question. Yes, if I understand your question correctly. The first sentence of 240.4 requires that conductors be protected based on their ampacities. If adjustment or correction factors (what was previously referred to as derating) need to be applied and the resulting ampacity is now less than the overcurrent device rating, you are not allowed to round up to the next rating for branch circuits with multiple receptacles as stated in 240.4(B).

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