How about when it is used for SERVICE EQUIPMENT? I have always used a service equipment rated disconnect or enclosed breaker as the first throw on a service. Most discos that are not service equipment rated have no means of grounding the neutral.
225.31 Disconnecting Means. Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure. 225.36 Suitable for Service Equipment. The disconnecting means specified in 225.31 shall be suitable for use as service equipment. Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.
I would think that about covers it. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison