Generator single line diagrams
A generator single line diagram shows how a standby or portable generator connects to the building and how it is kept from backfeeding the utility. It shows the generator and its breaker, the transfer equipment, the panels it feeds and where the neutral is bonded.
The templates cover a portable generator inlet with a breaker interlock, a manual transfer switch for selected circuits, automatic transfer switches for whole-home and essential-loads backup, a 400A service with a 200A generator, and a commercial four-pole transfer switch.
6 generator single line diagram templates
Portable generator inlet with interlock
Backfed 30A breaker mechanically interlocked with the main.
GeneratorView drawing
Generator with manual transfer switch
Ten-circuit manual transfer switch with an inlet box.
GeneratorView drawing
Standby generator, whole-home ATS
Service-rated 200A automatic transfer switch.
GeneratorView drawing
Standby generator, essential loads panel
100A transfer switch feeding an essential loads subpanel.
GeneratorView drawing
400A service with ATS and 200A generator
Service-rated 400A transfer switch feeding two 200A panels.
GeneratorView drawing
Commercial standby generator with ATS
Four-pole transfer switch feeding a standby panel at 120/208V.
GeneratorView drawingWhat the reviewer looks for
- The transfer equipment: an interlock, a manual transfer switch or an automatic transfer switch, with its amp rating.
- Whether the transfer switch is service rated. If it is, it becomes the service disconnect and the panel after it becomes a subpanel with isolated neutrals.
- The generator output current and the breaker protecting it, such as 22 kW ÷ 240V = 92A, protected at 100A.
- Whether the transfer switch switches the neutral. If it does, the generator is a separately derived system, bonded and grounded at the generator.
- Load shedding or load management where the calculated load can exceed the generator rating.
The ratings on the templates are typical values, not a design for your job. Confirm what your authority having jurisdiction and your utility expect before you submit.
Questions about generator drawings
How do you show a transfer switch on a single line diagram?
As a box with two source terminals, normal (N) and emergency (E), and one load terminal, tagged ATS for automatic or MTS for manual. The utility feeds the normal side, the generator feeds the emergency side and the load side feeds the panel. Label it with its amp rating and say whether it is service rated.
Does a portable generator with an interlock need a single line diagram?
Many inspectors ask for a simple one. It shows the inlet box, the backfed generator breaker, the listed mechanical interlock with the main breaker and how the generator neutral is arranged. Check what your authority having jurisdiction expects.
Other single line diagram templates
Draw yours now
Free, in the browser, no account. Start from a template or describe the job in plain words, edit the drawing and export a PDF.