National Electrical Installation Standards

Standards as High as Your Own

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Friday, May 8, 2020

Question:

Hello NEC Friends,

Like all state, thanks for the code of the day. This question is a caveat to today’s question, does the code allow you to say strip out 6/2 NM and use it in a piping system but now use the 75 C column for 65 amps instead of the 60C at 55 amps. Thanks, and best to all during these trying times. Be a good neighbor and citizen.


Butch Gosselin
A

Answer:

Hi Butch,

Thanks for the question and the remarks. Section 334.80 covers the ampacity for NM cables. It indicates that the ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The allowable ampacity shall not exceed that of a 60°C (140°F) rated conductor. The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction calculations, provided the final calculated ampacity does not exceed that of a 60°C (140°F) rated conductor. Final ampacity after ampacity adjustment or correction calculations is limited to 55 amperes. Hope this is helpful.

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