A 480-VAC wall-mounted assembly with a main MCCB and branch MCCBs, rated 600 A for the main and 125 A for the branches, is a panelboard.

• A. Panelboard
• B. Switchgear
• C. Bus Duct
• D. Distribution Panel

Answer: (A)

The main idea here is how to recognize a panelboard by its purpose and construction. A panelboard is an enclosed distribution device that sits inside a single cabinet and houses a main overcurrent protective device along with multiple branch-circuit protective devices. It is designed to take power from the source, through one main breaker, and distribute it to many branch circuits, all within one panel.

Seeing a wall-mounted 480-VAC assembly with a main MCCB rated for the overall panel (600 A) and several branch MCCBs rated lower (125 A) inside the same enclosure matches that definition. This setup is typical of a panelboard used to feed multiple branch circuits in a building or facility.

Switchgear, on the other hand, is generally larger and used for switching and protection of high-power feeders or motors, often with modular sections and not always in a single small wall-mounted panel. Bus duct is just the conductive distribution system (bus bars) within a duct or enclosure, not a panel containing multiple protective devices. And distribution panel is another term for the same concept as a panelboard; in this context panelboard is the precise term used.

So this assembly is a panelboard.