Standby generator, whole-home ATS single line diagram
Service-rated 200A automatic transfer switch. Use this for a permanently installed standby generator that backs up the whole house through a service-rated 200A automatic transfer switch.
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What the reviewer checks on this drawing
The reviewer checks the transfer switch as the new service disconnect, with the grounding electrode conductor and main bonding jumper landing there; the old main panel converted to a subpanel; the generator breaker; and load shedding if the calculated load is more than the generator can carry.
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 | 200A socket | Service conductors, per utility |
| Transfer switch | Automatic transfer switch | 200A · service rated, main disconnect inside | |
| Circuit breaker | 100A 2P | Generator breaker | |
| Generator | Standby generator | 22 kW · 120/240V, natural gas | |
| Panel | Main panel | 200A bus · neutrals isolated | 3 #3/0 Cu + #6 G |
| Circuit breaker | Existing | All house loads | |
| Load | Existing loads |
Notes on the sheet
- Transfer switch is the service disconnect. Grounding electrode conductor and main bonding jumper terminate at the transfer switch.
- Existing main panel becomes a subpanel: isolate neutrals and remove the bonding screw.
- Generator 22 kW ÷ 240V = 92A, protected at 100A.
- Load shedding modules added if the calculated load exceeds the generator rating.
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.
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