Which statement best describes panelboard rating and main breaker in low-voltage distribution?

• A. Panelboard rating determines fault current capability and main breaker simply disconnects the service.
• B. Panelboard rating sets the service voltage and main breaker controls voltage drop.
• C. Panelboard rating indicates maximum current; main breaker provides overcurrent protection and a disconnect for the main service.
• D. Panelboard rating is decorative; main breaker is the only protective device.

Answer: (C)

The essential idea is that the panelboard rating is the maximum current the panel and its conductors are designed to carry, while the main breaker provides overcurrent protection and serves as the service disconnect for the entire panel.

The panelboard rating sets how much current can flow safely through the bus and wiring in normal and fault conditions; it does not set the service voltage—that value comes from the supply and equipment installed. The main breaker is there to interrupt excess current to protect the wiring and devices, and it also functions as the main means to disconnect the service for safety or maintenance.

The other statements mix up roles: panelboard rating does not determine service voltage, and saying it sets fault current capability oversimplifies and misses the main protective function of the breaker. Calling the panelboard rating decorative is obviously incorrect.