What is the minimum rating for a service disconnecting means for a building, other than a single-family dwelling, with three 2-wire circuits?

The most appropriate choice for the minimum rating of a service disconnecting means in a building other than a single-family dwelling with three 2-wire circuits is 60 amperes. The National Electrical Code (NEC) specifies minimum service capacity for different types of electrical setups.

In this case, each 2-wire circuit typically provides a 15 or 20 amp profile, depending on the size of the circuit conductors used. For three circuits, this adds up to a minimum load that would require a service disconnect that can handle at least 60 amperes. This rating ensures sufficient capacity to manage the overall electrical load safely while allowing for some additional headroom beyond just the calculated demand of the circuits themselves.

Furthermore, installing a disconnect rated at 60 amperes is also in compliance with NEC standards for multi-family or commercial buildings, ensuring that the electrical system is adequately equipped to supply higher loads that are often present in these types of structures. A lower rating, such as 30 or 45 amperes, would likely be inadequate for the overall demand and usage scenarios typical in a multi-circuit environment.