Services & DistributionQuestion 72 of 521
The interrupting rating of an overcurrent device must be:
a.Equal to the load current
b.At least 65,000 A in all cases
c.Equal to the conductor ampacity
d.Not less than the available fault current at its line terminals
Explanation
Per 110.9, equipment intended to interrupt current at fault levels must have an interrupting rating at least equal to the available fault current at its line terminals. A device with too low an interrupting rating can fail catastrophically. Load current and conductor ampacity are unrelated to interrupting rating.
Law Reference: 2023 NEC §110.9Practice all 521 questions free — no signup required.
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