This standard applies to enclosed low-voltage ac power circuit breakers as described in American National Standard for Low-Voltage AC Power Circuit Breakers Used in Enclosures, C37.13-1973 (IEEE Std 20-1973), except that the circuit breakers discussed in this standard incorporate current-limiting fuses as an integral part of the circuit breaker. The entire device thereby becomes capable of interrupting shortcircuit currents up to 200 000 A rms and may be applied on circuits where the available short-circuit current does not exceed that amount.

This standard applies to enclosed low-voltage ac power circuit breakers as described in American National Standard for Low-Voltage AC Power Circuit Breakers Used in Enclosures, C37.13-1973 (IEEE Std 20-1973), except that the circuit breakers discussed in this standard incorporate current-limiting fuses as an integral part of the circuit breaker. The entire device thereby becomes capable of interrupting short circuit currents up to 200 000 A rms and may be applied on circuits where the available short-circuit current does not exceed that amount.