CSLB C-10 Electrical ContractorEquipment and InstallationMedium
An electrician installs a multiwire branch circuit consisting of two ungrounded conductors and a shared neutral, supplying receptacles in a kitchen. The circuit uses two single-pole circuit breakers without a handle tie or common-trip mechanism. Does this installation comply with NEC 210.4(B)?
- ANo, a means must be provided to simultaneously disconnect all ungrounded conductors at the panelboard, such as a handle tie or common-trip breaker.
- BYes, single-pole breakers are always acceptable for multiwire branch circuits.
- CNo, multiwire branch circuits are prohibited entirely in dwelling units.
- DYes, as long as the neutral conductor is oversized.
Show answer & explanationAnswer & explanation
Correct answer: A. No, a means must be provided to simultaneously disconnect all ungrounded conductors at the panelboard, such as a handle tie or common-trip breaker.
NEC 210.4(B) requires that multiwire branch circuits be provided with a means to simultaneously disconnect all ungrounded conductors at the panelboard, using either identified handle ties or a common multipole breaker, so that the circuit cannot be de-energized on only one leg while the other remains energized.
Why the other options are wrong
- B. Single-pole breakers without a simultaneous disconnect means do not meet 210.4(B).
- C. Multiwire branch circuits are permitted in dwellings when properly installed, not prohibited.
- D. Neutral conductor sizing does not satisfy the simultaneous disconnect requirement.
Multiwire Branch Circuit Disconnect (210.4(B))
Multiwire branch circuits must have a means to simultaneously disconnect all ungrounded conductors at the panelboard where the circuit originates.
- Handle ties or common-trip breakers satisfy the requirement
- Prevents energized neutral hazards during single-pole servicing
- Applies wherever a shared neutral serves two or more ungrounded conductors
Memory trick: 'Tie the handles so both legs die together.'