The largest permitted ITCB breaker for Motor 1 is what amperage?

The largest permitted ITCB breaker for Motor 1 is what amperage?

• A. 70
• B. 60
• C. 40
• D. 35

Answer: (A)

Protecting a motor with a circuit breaker is all about sizing the device to handle the motor’s normal startup surge but still trip during a fault. For motor branch protection with a breaker, the maximum allowable size is 250% of the motor’s full-load current (FLC). Multiply the motor’s FLC by 2.5 to obtain the largest permitted breaker rating. If Motor 1 has an FLC of 28 A, then 28 × 2.5 equals 70 A. So the greatest ITCB you can use for Motor 1 is 70 A. This ensures adequate protection for conductors and the motor while avoiding nuisance tripping during normal startup.

Protecting a motor with a circuit breaker is all about sizing the device to handle the motor’s normal startup surge but still trip during a fault. For motor branch protection with a breaker, the maximum allowable size is 250% of the motor’s full-load current (FLC). Multiply the motor’s FLC by 2.5 to obtain the largest permitted breaker rating.

If Motor 1 has an FLC of 28 A, then 28 × 2.5 equals 70 A. So the greatest ITCB you can use for Motor 1 is 70 A. This ensures adequate protection for conductors and the motor while avoiding nuisance tripping during normal startup.