Panelboard rating for incoming service 277/480?

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Multiple Choice

Panelboard rating for incoming service 277/480?

Explanation:
Panelboard rating is the ampacity—the maximum continuous current the busbars and enclosure are designed to carry. For a 277/480V service, the panelboard is typically specified with a 600 A bus rating. This matches common service sizes and lets the main disconnect and feeders be sized accordingly while staying within the panel’s safe current-carrying capability. The other options don’t fit because 250 A is a smaller ampacity than usual for a 480V service, and 480 and 277 are voltages (line-to-line and line-to-neutral), not the panel’s current rating.

Panelboard rating is the ampacity—the maximum continuous current the busbars and enclosure are designed to carry. For a 277/480V service, the panelboard is typically specified with a 600 A bus rating. This matches common service sizes and lets the main disconnect and feeders be sized accordingly while staying within the panel’s safe current-carrying capability. The other options don’t fit because 250 A is a smaller ampacity than usual for a 480V service, and 480 and 277 are voltages (line-to-line and line-to-neutral), not the panel’s current rating.

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