CSLB C-10 Electrical ContractorWiring Methods and MaterialsMedium
A residential kitchen circuit uses a multiwire branch circuit with two ungrounded conductors sharing a common neutral, feeding two separate 120V receptacle circuits. Per NEC 210.4(B), what is required at the panelboard?
- ATwo separate neutral bars, one for each circuit
- BNo special disconnect provisions since the conductors are separately labeled
- CA means to simultaneously disconnect both ungrounded conductors, such as identified handle ties or a two-pole breaker
- DA dedicated GFCI breaker installed only on the neutral conductor
Show answer & explanationAnswer & explanation
Correct answer: C. A means to simultaneously disconnect both ungrounded conductors, such as identified handle ties or a two-pole breaker
NEC 210.4(B) requires that all ungrounded conductors of a multiwire branch circuit be provided with a means to disconnect them simultaneously at the panel, typically via handle ties on single-pole breakers or a two-pole breaker, to prevent the neutral from carrying unbalanced current when only one circuit is de-energized.
Why the other options are wrong
- A. Splitting neutral bars does not address the disconnect requirement and is not code-compliant for a shared neutral.
- B. Labeling alone does not meet the code-mandated safety requirement.
- D. GFCI protection does not satisfy the simultaneous disconnect requirement.
Multiwire Branch Circuit Disconnect (210.4B)
Multiwire branch circuits must have a means to disconnect all ungrounded conductors simultaneously to protect against overloading the shared neutral.
- Handle ties or two-pole breakers satisfy this requirement
- Protects against neutral overcurrent if one circuit is serviced while the other remains live
- Applies to circuits sharing a neutral across two ungrounded conductors
Memory trick: Tie the handles so the neutral never overloads alone.