Services & DistributionQuestion 29 of 521
A service uses 3/0 copper conductors at 75 C (200 A ampacity) with a 200 A load. What is the correct standard OCPD?
a.225 A
b.250 A
c.175 A
d.200 A
Explanation
The conductor ampacity (200 A) exactly matches a standard OCPD rating, so a 200 A device is used - the next-size-up rule of 240.4(B) does not apply when the ampacity equals a standard size. 175 A undersizes for the 200 A load, and 225/250 A overprotect the conductor.
Law Reference: 2023 NEC §240.6(A)Practice all 521 questions free — no signup required.
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