The NEC has a requirement that LVCBs have an inst. trip. Does this mean that one must have inst. trips on mains and ties, or only on feeders? Does this mean the main and tie circuit breakers must be equipped with a maintenance switch to provide s fast trip in the event of a fault? If the existing main lacks a maintenamce switch, and has only a short time trip, can the client retain that circuit breaker in operation? Can the main or tie be equipped with a short time only trip, no inst. under normal conditions, but a maintenance switch to use if someone is working on the load side equipment?