Which conductors must the service disconnect be able to disconnect?

• A. All ungrounded conductors.
• B. The neutral conductor only.
• C. All conductors including grounded and neutrals.
• D. Only the ground conductors.

Answer: (A)

The main idea is that the service disconnect must be able to interrupt the conductors that actually carry power from the utility—the ungrounded conductors. These are the hot wires that energize the installation. The neutral is a grounded conductor used as a return path and is bonded to ground at the service equipment, so it isn’t what the disconnect is designed to open. The equipment grounding conductor is a safety path that should stay connected and not be switched. If the disconnect only opened the neutral or only the grounds, the live hot conductors would remain energized, which is unsafe. So, the service disconnect is intended to disconnect all ungrounded conductors.