Issue:
Ampere rating of the primary main circuit breaker cannot be selected

Product Line:
Hospital Isolated Power Systems

Environment:
NFPA 99, NEC 517.160

Cause:
The ampere rating of the primary main circuit breaker cannot be changed.

Resolution:
Medical panels are tested and UL Listed as a complete piece of equipment and the primary main breaker size is specified by UL; therefore, the customer does not have the option of specifying the breaker size. UL1047 Art. 23.1 Overcurrent protection provided for the primary circuit shall be rated not more than 125% of the ampere rating of the primary circuit.  Exception: The next higher standard rating is acceptable if 125% of the ampere rating does not correspond to a standard rating of a fuse or circuit breaker. For a transformer rated less than 1000 VA, the overcurrent protection shall not be rated more than 167% of the primary current. Conclusion: The panel cannot bear a UL mark if furnished with a main circuit breaker rating exceeding the value specified by UL.

Released for: Schneider Electric USA