What is the maximum overload protection size, based on 430.32(A)(1), for a 480-Volt, 25-horsepower, 3-phase motor marked with a 1.15 service factor and a nameplate current of 32 amperes? Assume this selection will permit the motor to start and the sizing per 430.32(C) is not warranted.

• A. 32 A
• B. 36.8 A
• C. 40 A
• D. 44.8 A

Answer: (C)

In motor circuits, overload protection must be sized not to exceed 125% of the motor’s full-load current. The motor’s full-load current on the nameplate is 32 A, so 1.25 × 32 = 40 A. The largest standard protection size that stays within this limit is 40 A, making it the maximum overload protection size. The 44.8 A option would exceed the limit, while smaller options are allowed but not the maximum. The service factor (1.15) indicates the motor can handle a bit more than rated briefly, but it doesn’t change the 125% limit for overload protection in this scenario, and we’re not applying 430.32(C) here.