Template · Generators

400A service with ATS and 200A generator single line diagram

Service-rated 400A transfer switch feeding two 200A panels. Use this for a large home with a 400A service: one service-rated 400A transfer switch feeds two 200A panels, backed by a 200A generator.

A free template with typical ratings, conductor callouts and general notes. Open it, change what differs on your job, fill in the title block and export a PDF.

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400A service with ATS and 200A generator single line diagram: service-rated 400A transfer switch feeding two 200A panels. — 400A service with ATS and 200A generator. 9 devices on an 11 × 17 in sheet with a title block and notes column.

What the reviewer checks on this drawing

The reviewer looks for load management where the two panels together can exceed the generator, and for both panels wired as subpanels downstream of the transfer switch.

What the drawing shows

Every device on the sheet, in the order power reaches it.

Symbol	Label	Rating or detail	Conductors feeding it
Utility source	Utility service	120/240V 1φ 3W
Meter	Utility meter	320A socket (CL320)	Service conductors, per utility
Transfer switch	Automatic transfer switch	400A · service rated
Circuit breaker	200A 2P	Generator breaker
Generator	Standby generator	48 kW · 120/240V, liquid cooled
Circuit breaker	200A 2P	Panel A feeder
Panelboard	Panel A	200A
Circuit breaker	200A 2P	Panel B feeder
Panelboard	Panel B	200A

Notes on the sheet

Generator 48 kW ÷ 240V = 200A.
Load management required where the combined panel load can exceed the generator rating.
Both panels are subpanels downstream of the service-rated transfer switch.

Diagram is schematic and not to scale. Field-verify existing equipment ratings. Ratings and conductor sizes shown are typical. Confirm against the adopted code, the equipment listing and a load calculation before installation. Code references are to the 2023 NEC and the 2024 Canadian Electrical Code: see references and editions.