Interrupting capacity is the maximum amperage a circuit breaker can safely interrupt. Circuit breaker Interrupting capacity is the maximum amperage a circuit breaker can safely interrupt. Circuit breaker manufacturers publish this specification along with the number of times the circuit breaker will perform this feat. For example, E-T-A publishes two types of interrupting capacity specifications. One is called Icn, or Normal Interrupting Capacity –is the highest current the circuit breaker can interrupt repeatedly. The Normal Interrupting Capacity reflects the circuit breaker quality. The other specification is UL 1077 Interrupting capacity – which is defined as the maximum current a circuit breaker can safely interrupt at least one time without causing a fire hazard.