Q.When is a two-pole breaker required for a multiwire branch circuit?

A.Multiwire and multiple branch circuits that supply devices or equipment on the same yoke (also called a strap) must be provided with a means to disconnect simultaneously all ungrounded conductors that supply those devices or equipment [210.4(B) and 210.7(B)]. Individual single-pole circuit breakers with handle ties identified for the purpose — or a breaker with common internal trip — can be used for this application [240.20(B)(1)].

Note: The intent of this rule is to prevent people from working on energized circuits that they thought were disconnected from their source.