Technical FAQs

Ask a Question

Can a circuit breaker be applied on a circuit with a fault level above the circuit breaker's AIC rating?

Issue:
Can a circuit breaker be applied on a circuit with a fault level above the circuit breaker rating?  In other words, does a circuit breaker's interrupting rating have a tolerance?

Product Line:
MCCB and MCB

Resolution:
NEC article 110.9 states:
"Equipment intended to interrupt current at fault levels shall have an interrupting rating not less than the nominal circuit voltage and the current that is available at the line terminals of the equipment."
So, there is no tolerance for a circuit breaker being rated at any value less than the available fault current.
Was this helpful?
What can we do to improve the information ?