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Friday, May 22, 2015
Question:
NEC 240.21(C) does the provisions of 240.4(B) apply to this article or all transformer secondary conductors. Meaning you must size the conductors for the overcurrent device.
Donald Zasada
A
Answer:
The provisions of 240.4(B) "the conductor round up rule" are not allowed for feeder taps or transformer secondary conductors as stated in 240.21(B) and 240.21(C). The tap conductor ampacity must be "not less than" the overcurrent device or equipment being supplied. If secondary conductors have overcurrent protection where they receive their supply then 240.4(B) can be used if all the conditions are met.