Technical FAQs

Ask a Question

What are the rules for choosing an inverse-time circuit breaker for motor circuits?

Issue:
How to select a breaker for a motor circuit

Product Line:
Circuit Breakers

Resolution:
As stated in the NEC code, an inverse-time CB to be sized 250% of the motor FLA. If that will not start the motor, the size may be increased to 400% for FLA 100A or less, and to 300% for FLA greater than 100A. See NEC Table 430.52 and section 430.52.
Was this helpful?
What can we do to improve the information ?