What is a multiwire branch circuit?

• A. Only one feeder or branch circuit may be used to service a branch circuit or feeder on the load side of a service disconnecting means
• B. A knot
• C. A type of insulator
• D. A kind of lamp

Answer: (A)

A multiwire branch circuit is built from two or more ungrounded conductors that share a single neutral. In a typical 120/240-volt system, these hot conductors come from different phases so the neutral only carries the difference in current between them. This lets you run more loads with fewer wires, since the shared neutral handles the imbalance rather than a separate neutral for each circuit.

A key safety point is that all ungrounded conductors in this arrangement must be disconnected simultaneously, using a common-trip or handle-tied breaker, so the neutral cannot be energized if one circuit is turned off. The neutral is sized to carry only the imbalance current, not the full sum of the two circuits, and the conductors sharing the neutral are generally run together to ensure proper operation and safety.