HOLT Electricians Practice Exam

For motors with a service factor (SF) rating of 1.15 or more, the overload protection device must be sized at no more than what percentage of the motor nameplate current rating?

1. 100%

2. 115%

3. 125%

4. 150%

The correct answer is: 125%

For motors with a service factor (SF) rating of 1.15 or more, the overload protection device is designed to be sensitive to the operating conditions of the motor while providing adequate protection from overheating. A service factor greater than 1 indicates that the motor is capable of handling some overload without suffering damage. The National Electric Code (NEC) suggests that for motors with a service factor of 1.15, the overload protection should be sized to respond to the motor's nameplate rating effectively. By sizing the overload protection at 125% of the motor nameplate current rating, it allows the motor to operate at its full rated capacity, accounting for the extra tolerance provided by the service factor. This means if the motor's current draw exceeds that 125% threshold, the overload protection will engage, preventing potential damage due to overheating during operation. Understanding this percentage is crucial for ensuring both the functionality and the safety of the motor in real-world applications, particularly when it operates under varying loads.