What is a branch circuit with two or more un-grounded conductors called when it has equal voltage to a grounded conductor?

A branch circuit that includes two or more ungrounded conductors, all having equal voltage to a grounded conductor, is defined as a multiwire branch circuit. This configuration allows the conductors to share a single neutral conductor while still providing power. What makes a multiwire branch circuit particularly beneficial is that it can help to balance the load between the different phases, enabling more efficient use of the electrical system.

In typical residential or commercial applications, this wiring method can facilitate lighting and receptacle circuits while maintaining proper grounding and overload protection. It’s important to ensure that these circuits comply with National Electrical Code (NEC) requirements, particularly regarding overcurrent protection and neutral conductor sizing.