The trip rating of a circuit breaker used as the main protective device in a panel board cannot exceed?

The trip rating of a circuit breaker functioning as the main protective device in a panel board must not exceed the amperage capacity of the bus bars in the panel board. This limitation is critical for ensuring that the panel can safely handle the maximum current without risk of overheating or damage. If the trip rating of the circuit breaker exceeds the bus bars' capacity, it could result in a failure where the circuit breaker would not trip adequately during an overload condition, potentially leading to severe electrical hazards, including fire risks or equipment damage.

While the voltage of the incoming supply, the manufacturer's recommended amperage, and the load of all connected devices play essential roles in the overall design and safety of electrical systems, it is the bus bar capacity that directly dictates the safe operational limits of the circuit breaker. Exceeding the bus bar capacity would undermine the electrical system’s integrity and safety, highlighting why adherence to this guideline is crucial in electrical installations.