Most-missed NEC mock exam question #4 of 5, from JCR's free 25-question NEC mock exam. 67% of students got this wrong. Try it with your 2020 NEC open, then check your answer below.
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The answer: B, False
430.32(A)(1) sets a maximum, not a minimum. A separate overload device must be selected to trip, or be rated, at no more than a set percent of the motor nameplate current.
A 1.10 service factor is below 1.15, so the 125% row does not apply. The question gives no temperature rise, so this motor falls under "all other motors": 115% maximum.
Two traps in one question
- "At least" vs. "no more than." The 430.32 percentages are ceilings.
- 1.10 vs. 1.15. The 125% limit is only for a marked service factor of 1.15 or greater, or a marked temperature rise of 40°C or less.
The same question with numbers
Say the 5 hp motor's nameplate reads 15.2 A, with a 1.10 service factor and no temperature rise marked:
- 1.10 is below 1.15, so it's an "all other motors" case: 115%.
- 15.2 A × 115% = 17.48 A maximum for the overload.
- Setting it at 125% (19 A) would go over that limit. That's why the statement is false.
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Start with the nameplate current
Separate overload protection is based on the motor nameplate current rating (430.6(A)(2)). Breakers and branch-circuit conductors are the opposite: for most motors, they use the NEC table current (430.6(A)(1)).
The limits
| Motor nameplate shows | Maximum, 430.32(A)(1) | Maximum if it won't start or carry the load, 430.32(C) |
|---|---|---|
| Service factor 1.15 or greater | 125% | 140% |
| Temperature rise 40°C or less | 125% | 140% |
| All other motors | 115% | 130% |
- More than 1 hp, continuous duty: 430.32(A)(1).
- 1 hp or less, automatically started: 430.32(B)(1) sends you to the same 430.32(A)(1) limits.
- 1 hp or less, nonautomatically started: 430.32(D).
- The higher limits are in 430.32(C). Older study materials cite 430.34 for them, but in the 2020 NEC they are in 430.32(C). If the overload device is not shunted during starting under 430.35, it must have enough time delay to let the motor start and accelerate its load.
There is no next-size-up allowance in 430.32(A)(1) like the one breakers get in 430.52. If the device can't start the motor or carry the load, 430.32(C) is the only increase, and it has its own ceiling.
Worked example
A 10 hp motor, nameplate current 28 A, service factor 1.15:
- 28 A × 125% = 35 A maximum.
- If that won't start the motor or carry the load: 28 A × 140% = 39.2 A maximum.
Bonus: a related question from JCR's full mock exam
This one is not part of the free exam. A 1 hp, automatically started motor with a 30°C temperature rise is protected by an overload relay that won't carry the starting current. How high can the relay go?
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- 1 hp, automatically started: 430.32(B)(1), which uses the 430.32(A)(1) limits.
- 30°C is 40°C or less: the 125% row.
- The relay won't carry the starting current, so 430.32(C) applies: 140%.
41% of students got this one wrong, and 125% was the most common wrong pick. That is the normal limit, not the increased one.
Common questions
What does a 1.15 service factor mean for overload sizing?
A marked service factor of 1.15 or higher lets you set a separate overload device as high as 125% of the nameplate current. Below 1.15, with no temperature rise of 40°C or less marked, the limit is 115%.
Do you size overloads from the nameplate or the NEC table?
The nameplate. 430.6(A)(2) bases separate overload protection on the motor nameplate current. The NEC tables are for conductors and the branch-circuit breaker or fuses.
What if the overload trips while the motor starts?
430.32(C) lets you go higher, but never past 140% (1.15 service factor or 40°C rise) or 130% (all other motors) of the nameplate current.
Based on the 2020 NEC. Pick up the 2020 code book, or read it with a paid NFPA LiNK subscription. See which edition your state's exam uses.
JCR checked this against the 2020 NEC in NFPA LiNK on October 21, 2026.
Related guides: How to size the motor breaker (Table 430.52) · The 5 most-missed NEC mock exam questions · Ampacity derating step by step
The 5 most-missed NEC mock exam questions
- Pull box size for an angle pull (314.28)
- Continuous loads on a 100%-rated assembly (210.20(A))
- Breakers used as switches: SWD and HID (240.83(D))
- Motor overload sizing and service factor (430.32) (this post)
- Closet light clearance (410.16(C))
See all 5 most-missed questions on one page.
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