For continuous-duty motors with service factor 1.15 and more than 1 horsepower, must a separate motor overload device be used and rated at no more than 125 percent of the full-load current?

For continuous-duty motors with service factor 1.15 and more than 1 horsepower, must a separate motor overload device be used and rated at no more than 125 percent of the full-load current?

• A. Yes
• B. No
• C. Only for motors over 50 hp
• D. Only if outdoors

Answer: (A)

Continuous-duty motors must have protection against overheating, and when a separate motor overload device is used, its rating is tied to the motor’s full-load current. For a continuous-duty motor with a service factor of 1.15 and more than 1 hp, the rule requires a separate overload device in the motor circuit. That device must be rated at no more than 125% of the motor’s full-load current. This sizing strikes a balance: it won’t nuisance-trip during normal startup or due to the service factor, yet it will trip if the current stays high long enough to overheat the windings. Therefore, installing a separate overload device with the 125% cap is required in this scenario.

Continuous-duty motors must have protection against overheating, and when a separate motor overload device is used, its rating is tied to the motor’s full-load current. For a continuous-duty motor with a service factor of 1.15 and more than 1 hp, the rule requires a separate overload device in the motor circuit. That device must be rated at no more than 125% of the motor’s full-load current. This sizing strikes a balance: it won’t nuisance-trip during normal startup or due to the service factor, yet it will trip if the current stays high long enough to overheat the windings. Therefore, installing a separate overload device with the 125% cap is required in this scenario.