Equipment & SystemsQuestion 266 of 521
Why must a motor circuit have both overload protection AND short-circuit/ground-fault protection?
a.They are the same device required in two locations
b.Overload devices protect against sustained overcurrents from motor running conditions, while short-circuit/ground-fault devices clear high-magnitude faults
c.Overloads clear faults faster than breakers
d.Short-circuit devices also sense motor running overload
Explanation
Overload devices (sized ~115-125% of FLA) protect the motor and conductors from sustained overloads but are too slow for faults; branch-circuit short-circuit/ground-fault devices (sized much higher per Table 430.52) clear high fault currents. NEC 430 requires both because each addresses a different hazard.
Law Reference: 2023 NEC §430.31Practice all 521 questions free — no signup required.
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