HOLT Electricians Practice Exam

For motors with a service factor of 1.10, the overload protection device must be sized at no more than what percentage of the motor nameplate ampere rating?

1. 100%

2. 110%

3. 115%

4. 125%

The correct answer is: 115%

The correct percentage for sizing the overload protection device for motors with a service factor of 1.10 is 115% of the motor's nameplate ampere rating. This service factor indicates that the motor can handle a temporary overload up to 10% above its rated capacity without sustaining damage. As a result, when sizing the overload protection, it's crucial to account for this capacity. The National Electrical Code (NEC) typically allows the overload protection to be set at a maximum of 115% of the motor nameplate rating for motors with a service factor. This threshold ensures the motor is adequately protected against overheating and potential damage by allowing for a slight margin for brief overload conditions but not so much that it risks failure during extended overload scenarios. Choosing 100%, 110%, or 125% would not align with the NEC recommendations for a service factor of 1.10, as these percentages either do not allow for adequate overload capacity or exceed safe limits. Therefore, 115% provides the right balance for efficient operation and protection.