Quote:
Originally Posted by ViribusUnitis  I... I guess 30A might be enough at stable, but I would have been expecting the a/c to be triping the shore breaker all the time. |
Quote:
Originally Posted by Beausoleil But that surge is only short term - it usually won't trip the 30A shorepower breaker... |
Molded case
circuit breakers have an inverse time-delay characteristic (specified on a time-current curve*), and an instantaneous trip mechanism which responds to a predetermined value of overload without any purposely delayed action (generally a short circuit).
Only reference to the specific breaker’s time-current curve, and the load’s starting current specifications, will determine whether the breaker will delay tripping long enough to permit the equipment to start.
However,
I wouldn’t expect most 30A 2P circuit breakers, used on boats, to "nuisance" trip upon typical (short time) 40A A/C inrush currents, even when combined with other loads to a total of 50A (momentary).
Selective coordination is the selection and application of circuit protective devices in series, such that under overload or fault current conditions, only the device just up stream from the overload or fault (branch cct. breaker) will open to clear the fault. The remainder of the circuit’s protective devices (main breaker) will remain closed passing power to their individual loads. Selectivity can be based upon time or current levels.
* Time current curves are plots of the amount of current (vertical scale) flowing in the circuit to the time (horizontal scale) required for the breaker to clear the fault current.