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Monday, July 15, 2019
Question:
Hi Charlie!
I appreciate everything you are doing and enjoy the daily code questions. What types of conductors and circuits does 240.4(B) apply to? Service and panel feeders, sub panel feeders, motor circuits, what types of branch circuits?
Thank you for your time!
Respectfully, Timothy J. Rein
A
Answer:
Hey Timothy thanks for your question and the kind words. Section 240.4 is an overcurrent rule that applies to conductors other than flexible cords, flexible cables, and fixture wires because they are covered by 240.5. It applies to conductors that are not covered by other rules which includes service, feeder and branch circuits. The NEC does not differentiate between feeders and sub-panel feeders, they are all feeders. Often referred to as a "round up rule", 240.4(B) allows the next higher standard overcurrent device rating to be used if the conditions stated are met.
Flexible cords flexible cables, and fixture wires, do not have a round up rule in 240.5. For service conductors 230.90 Exception 2 refers back to 240.4(B) and 430.52 Exception 1 is for motor circuits. Keep in mind that the conductors must be large enough for the load as stated in 210.19, 215.2 and 230.46 and also the rule for small conductors in 240.4(D).