Lesson 6 · Motor Control

Hand-Off-Auto

One selector switch, three positions, and a circuit that can run by hand or run itself. Hand-Off-Auto is on nearly every industrial panel — and it's a clean payoff for everything you've learned.

What it does

A Hand-Off-Auto (HOA) selector is a maintained, three-position switch that gives an operator a choice about how a motor is controlled:

HAND — run the motor manually, right now, regardless of any automatic device. Used for testing, maintenance, or forcing operation.
OFF — the motor can't run no matter what. A true off, in the middle.
AUTO — hand control over to an automatic device (a float, a thermostat, a pressure switch, a PLC). The motor runs when that device calls for it.

The selector's common feeds either the HAND path (straight to the coil) or the AUTO path (through an automatic device). OFF connects to neither.

How it's wired

The selector has one common terminal (fed from the hot side of the control circuit) and it routes that common to one of two outputs depending on position:

In HAND, the common connects straight to the coil — the motor runs immediately, bypassing any automatic device.
In OFF, the common connects to neither output. Dead. The motor can't run.
In AUTO, the common connects through the automatic device (a float switch, pressure switch, PLC output) to the coil. Now the motor follows that device.

Both the HAND path and the AUTO path land on the same coil — they're just two different routes to energize it. The selector picks which route is live.

Why it's everywhere: HOA lets a tech force a pump on by hand to test it, lock it OFF for service, then return it to AUTO so it runs on its own — all from one switch, without touching the wiring. It's the practical bridge between manual and automatic control.

Combining with start/stop

On bigger systems you'll see HOA combined with the three-wire start/stop you already know: AUTO might feed a full seal-in circuit, while HAND gives a direct manual run. The principle stays the same — the selector is choosing which control logic gets to energize the coil. Everything you learned about seal-ins, overloads, and contactors still applies; HOA just adds a layer of operator choice on top.

What to take away

Hand-Off-Auto is a three-position maintained selector that routes control power to either a manual path (HAND), nothing (OFF), or an automatic device (AUTO). It's how one panel serves both the operator who needs to force a machine and the process that needs to run itself. Master this and you can read the control scheme on most industrial equipment you'll meet.

Now build it yourself

In the Sandbox: wire a Selector (H-O-A) common to your control hot. Run its T1 (HAND) straight to Coil "M", and its T2 (AUTO) through a Float or Limit switch to the same coil. Cycle the selector through Hand, Off, and Auto and watch how the motor's behavior changes.

Open the Sandbox →