Equipment & SystemsQuestion 253 of 521
A motor disconnecting means must have an ampere rating at least 115% of the motor FLC. For a 15 HP, 460 V, three-phase motor (FLC 21 A), what is the minimum disconnect ampere rating?
a.24.15 A
b.21 A
c.26.25 A
d.18.9 A
Explanation
NEC 430.110(A) requires the disconnecting means to be rated at least 115% of the FLC: 21 x 1.15 = 24.15 A. 21 A ignores the 115% factor, 26.25 A is 125%, and 18.9 A is 90%.
Law Reference: 2023 NEC §430.110Practice all 521 questions free — no signup required.
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