What feature must every multi-wire branch circuit have regarding ungrounded conductors?

In a multi-wire branch circuit, it is essential that all ungrounded conductors have simultaneous disconnection. This requirement is crucial for safety to ensure that when the power is turned off, all the conductors are disconnected at the same time, minimizing the risk of shock or electrical hazards.

The simultaneous disconnection feature prevents situations where one ungrounded conductor remains live while another is turned off, which could lead to dangerous conditions when working on the circuit. By requiring that all ungrounded conductors are disconnected simultaneously, the risk of electrical shock is significantly reduced, allowing for safer maintenance and repair work.

Other features such as independently switchable disconnects, manual reset switches, or interlock mechanisms do not provide the same level of safety specifically aimed at the synchrony of disconnection for multi-wire branch circuits. These methods may have their own applications and benefits, but they do not specifically address the necessity for all ungrounded conductors to be disconnected at the same time when the circuit is switched off.