What is a subpanel?

• A. A main service disconnect located outside the building.
• B. A panel used solely for outdoor lighting.
• C. A device that protects a single branch circuit from overload.
• D. A distribution panel fed from the main service or another panel.

Answer: (D)

A subpanel is a secondary distribution panel that is fed by a feeder from the main service panel (or from another panel) and then distributes circuits to different parts of the building. It’s typically located away from the main panel to expand the electrical system. The subpanel contains its own breakers for the circuits it serves, but the service disconnect device remains at the main service equipment. In a properly configured subpanel, the neutral bus is isolated from the grounding bus, with a grounding conductor running back to the service equipment.

This is why the correct choice describes a distribution panel fed from the main service or another panel. It’s not the main service disconnect, not a panel used solely for outdoor lighting, and not just a device protecting a single branch circuit.