Which device is considered an approved disconnecting means for ungrounded conductors that pass through buildings?

Which device is considered an approved disconnecting means for ungrounded conductors that pass through buildings?

• A. Circuit breaker
• B. Fused disconnect switch
• C. Lighting contactor
• D. Plug-in receptacle

Answer: (A)

When conductors that carry current but have no neutral return (ungrounded conductors) pass through a building, there must be an approved way to disconnect all of them quickly and safely at a readily accessible location. A circuit breaker is designed as a listed disconnecting means that can simultaneously interrupt all ungrounded conductors and also provides overcurrent protection. This dual function makes it the standard, recognized device for isolating power when entering or leaving a building, ensuring workers can de-energize the system before service or maintenance. A plug-in receptacle isn’t an approved disconnecting means for feeders or ungrounded conductors, because unplugging doesn’t reliably guarantee isolation of all conductors and it isn’t designed to interrupt under load. A lighting contactor is a control device used to switch small circuits or multiple lights, not a proper service or feeder disconnect. A fused disconnect switch can serve as a disconnect, but circuit breakers are the common, preferred option because they provide both disconnection and overcurrent protection in a listed, readily accessible form.

When conductors that carry current but have no neutral return (ungrounded conductors) pass through a building, there must be an approved way to disconnect all of them quickly and safely at a readily accessible location. A circuit breaker is designed as a listed disconnecting means that can simultaneously interrupt all ungrounded conductors and also provides overcurrent protection. This dual function makes it the standard, recognized device for isolating power when entering or leaving a building, ensuring workers can de-energize the system before service or maintenance.

A plug-in receptacle isn’t an approved disconnecting means for feeders or ungrounded conductors, because unplugging doesn’t reliably guarantee isolation of all conductors and it isn’t designed to interrupt under load. A lighting contactor is a control device used to switch small circuits or multiple lights, not a proper service or feeder disconnect. A fused disconnect switch can serve as a disconnect, but circuit breakers are the common, preferred option because they provide both disconnection and overcurrent protection in a listed, readily accessible form.