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Friday, October 2, 2015
Question:
I am wiring a commercial building using NM cable. The AC condensers call for MCA of 20.1 amps. Can we round down on that calculation to use 12/2 cable?
Thank you, Mike Thill
A
Answer:
Hey Mike thanks for your question. I know we are quibbling about splitting amperes (not hairs) or as a friend says picking fly stuff out of pepper, but literally the answer is no. Section 440.6 states that the equipment rating be used to determine the conductor ampacity. Calculations are permitted to be rounded to the nearest whole number as stated in 220.5(B) but reading a plate is not doing a calculation. Seems the equipment manufacturer could have rounded but it appears they chose not to. Remember there are a lot of other rules in Article 334 that apply to the use of NM cable.