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Question:

A 4 hp 230 V single phase motor has a service factor of 1.15 and name plate current rating of 25 A. What size dual element fuse can be used to protect the motor from overloads, short circuit and ground faults?

A 30 A
Explaination

The motor name plate rating = 25 A
Refer NEC 430.32(A)(1) The overload protection of motor with service factor 1.15 and above shall have protective device with 125% of rated current.
Overload protection device rating = 25 x 1.25 = 31.25A
Refer NEC 240.6(A), the standard fuse ratings that can be used. In this case 30A fuse can be used to protect the motor