The combined rating of circuit breakers or fuses is permitted to be greater than what?

The combined rating of circuit breakers or fuses can indeed be greater than the ampacity of the service conductors. Ampacity refers to the maximum current an electrical conductor or device can carry before sustaining immediate or progressive deterioration. This means the circuit breakers or fuses can be rated higher than what the conductors can handle, allowing for factors such as short-term overloads or coordination with upstream protection devices.

It is important to recognize that while the circuit breakers or fuses may have a higher rating, the conductors' ampacity does ultimately limit the maximum continuous current that should be carried to avoid overheating and potential failure. This concept is crucial in ensuring the safety and integrity of the electrical system. Proper coordination between protective devices and conductors is essential to prevent damage to the wiring and equipment under fault conditions.

In contrast, the other options do not align with the criteria for the permissible ratings of circuit breakers or fuses relative to service conductors. For instance, the maximum load voltage primarily concerns voltage ratings rather than current ratings, while short-circuit ratings deal with the device's capacity to withstand fault conditions. Operating temperature pertains to thermal characteristics but does not directly relate to the ratings of protective devices in terms of conductor capacity.