AC disconnect interrupt ratings
Can anyone explain to me what the interrupting rating needs to be (and why) for the AC disconnect on a typical grid-tied system?
NEC 690.17 says that it needs to be "sufficient for the current available at the line terminals of the equipment" What is that?
My local inspector is saying that the interrupting current can be 12,500 amps which your average disconnect can't handle.
I thought the service panel limited the current to the value of the OCP device. I understand that the breaker is not rated to be used to interrupt fault currents, but should it not limit the current so the disconnect AIC rating doesn't have to be so high?
Another buddy says that we need to use at least 2.5 feet of 10ga wire between the breaker and the disconnect (in this 5kW case) to satisfy the AIC rating. Inspector is saying we need to add fuses to the system which, of course, the utility won't allow inside the disconnect as they lock it for safety reasons.
On this issue, John Wiles says: " many utility-interactive PV systems make the utility connection through a back-fed circuit breaker in an existing load center and the existing load center is designed to handle the available short-circuit currents. No additional current limiting is required." Who is correct???
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