Mini-circuit breakers (UL 1077 supplemental protectors) are suitable for motor branch-circuit short-circuit and ground-fault protection.

Mini-circuit breakers (UL 1077 supplemental protectors) are suitable for motor branch-circuit short-circuit and ground-fault protection.

• A. Yes
• B. No
• C. Only for small motors
• D. Only if used with fuses

Answer: (B)

The main idea here is that motor branch-circuit protection must be provided by devices listed and rated for motor protection, capable of handling both short-circuit and ground-fault conditions with appropriate interrupting capabilities. Mini-circuit breakers under UL 1077 are supplemental protectors, designed to give extra protection to equipment within a panel or device and not to serve as the primary protective device for a motor circuit. They typically have limited interrupting capacity and are not listed to provide the motor-specific protection required by NEC rules. For motor circuits, you need primary protection devices that are explicitly listed for motor short-circuit and ground-fault protection (such as properly sized fuses or motor-rated circuit breakers). So, mini-circuit breakers are not suitable as the motor branch-circuit protection.

The main idea here is that motor branch-circuit protection must be provided by devices listed and rated for motor protection, capable of handling both short-circuit and ground-fault conditions with appropriate interrupting capabilities. Mini-circuit breakers under UL 1077 are supplemental protectors, designed to give extra protection to equipment within a panel or device and not to serve as the primary protective device for a motor circuit. They typically have limited interrupting capacity and are not listed to provide the motor-specific protection required by NEC rules. For motor circuits, you need primary protection devices that are explicitly listed for motor short-circuit and ground-fault protection (such as properly sized fuses or motor-rated circuit breakers). So, mini-circuit breakers are not suitable as the motor branch-circuit protection.