On Mon, Feb 16, 2015, at 07:58 PM, James Cameron wrote:
> I'll take that as meaning the rated holding current is not printed,
> and that the breakers may well be designed for the rated holding
> current, and then labelled for the trip current.

Circuit breakers are required not to trip up to 113% of rating, and
required to trip at 145% of rating, within 2 hours. This is the thermal
part of the circuit breaker.

The time-current curve (Z, B, C, K, D, etc) specifies the current
required for instantaneous trip. I think these all follow the thermal
curve but have different magnetic (instantaneous trip) ratings,
typically 5 or 10 times the printed current rating. I forget what curve
your typical breaker in a household branch panel contains. But the
thermal trip follows the 113/145 percent, 2 hour spec.

Friendly regards, Bob

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