Hand-Off-Auto with pressure switch (dual control)
Selector-switch circuit that runs the compressor manually in HAND and lets the pressure switch or controller run it in AUTO.
Recip compressorsSmall rotary screwsPump-down / booster packages
Step 1 of 5
Step 1
Feed the selector
From
X1 through the E-stop
To
HOA common terminal
Conductor: 16 AWG
The E-stop stays ahead of the selector so OFF and E-STOP both kill everything downstream. A 3-position maintained selector is standard: HAND (1), OFF (2), AUTO (3).
Verify before moving on
- 120 V at the HOA common in all three positions
- 0 V with the E-stop latched
Aux contacts & feedback
- Use a spare NO aux to feed a run-hour meter so hours only accumulate while the motor is actually running.
- For a controller-run package, replace the pressure switch with the controller's dry run relay contact and keep the HOA as a service bypass.
- A NC aux wired to the controller gives it positive feedback that the starter dropped out.
Before you land a wire
- HAND must never bypass the high-temperature switch, overload, or E-stop.
- Two-wire (maintained) control restarts automatically after a power blip — confirm that is acceptable and that the machine has a restart warning if required.
Reference only. Terminal numbers vary by manufacturer — confirm against the actual device drawing and follow NEC/NFPA 79 and your site's electrical safety program.