Is there a maximum distance (explicitly stated or generally accepted) between a building disconnect and building? For instance - install a Circuit breaker at the secondary of a customer owned transformer (unit substation). Secondary feeder supplies the building. The building is the only load, and there are no alternate supplies to the building. The unit sub is roughly 20' from the building. Can the circuit breaker be my disconnect, feeding a MLO switchboard within the building? Application is 480V 3ph 3000A. I am not even certain I can get a MLO switchboard but assuming I can, would I need a separate disconnect anyway?