Standby generator, essential loads panel single line diagram
100A transfer switch feeding an essential loads subpanel. Use this when a smaller standby generator backs up only the essential circuits. A 100A transfer switch feeds an essential loads subpanel, and the main panel stays on utility power.
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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What the reviewer checks on this drawing
The reviewer checks the generator output and its breaker, the isolated neutrals in the essential loads panel, and the generator’s placement and clearances.
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 |
| Circuit breaker | 200A 2P | Main breaker | |
| Panel | Main panel | 200A bus · 120/240V | |
| Circuit breaker | Existing | Non-essential loads | |
| Load | Existing loads | ||
| Circuit breaker | 100A 2P | ATS feed | |
| Transfer switch | Automatic transfer switch | 100A · not service rated | 3 #3 Cu + #8 G |
| Circuit breaker | 60A 2P | Generator breaker | |
| Generator | Standby generator | 14 kW · 120/240V | |
| Panel | Essential loads panel | 100A MLO · 120/240V | |
| Circuit breaker | Branch | Essential circuits | |
| Load | Furnace, sump, fridge, lighting |
Notes on the sheet
- Generator 14 kW ÷ 240V = 58A, protected at 60A.
- Essential loads panel neutrals isolated from the enclosure.
- Generator placement and clearances per manufacturer instructions and the gas code.
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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