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Practice question · NEC 430.52
What Does a Motor Branch-Circuit Breaker Actually Protect Against?
Exam-style question (Sparky QOTD)
The branch-circuit overcurrent device sized from Table 430.52 provides ___ protection for the motor circuit.
A. short-circuit and ground-fault
B. overload
C. thermal
D. undervoltage
Answer: A) short-circuit and ground-fault.
Where to Find It
Open your Code book to 430.51 and 430.52. The branch-circuit device you size from Table 430.52 handles short-circuit and ground-fault protection only. Overload protection is a separate requirement under 430.32.
Why Two Devices
A motor can fail two different ways. A short circuit is violent and instant — that's the breaker's job. An overload is slow: the motor working too hard, heating up over minutes. A standard breaker won't catch that in time, which is exactly why the Code requires separate overload devices. The breaker doesn't do overloads — full stop.
The Trap
Choice B (overload) feels right because in a house, the breaker “is” the overload protection. Motors play by different rules — Article 430 splits the job in two, and the exam loves asking which half the breaker covers.
Exam Tip
If any question asks what protects a motor against overload, the branch-circuit breaker is never the answer. Look for the overload device per 430.32 instead.
Keep Drilling
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