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A 240-volt switch is wired as a double-pole device that interrupts both hot conductors at the same time.
For the full breakdown, see our best 240V Switch guide.
A 240-volt circuit carries two live legs, and a switch that breaks only one leaves the other hot — a shock waiting at the terminals. That’s why the answer to how to wire a 240-volt switch starts with double-pole hardware, then careful sequencing: power off, verify dead, wire to the diagram, test before you trust it. The same routine covers shop heaters, water pumps, and any other 240V load you want on a wall switch.
What Makes a 240-Volt Switch Different?
A 240-volt switch is different because it must open both 120-volt hot conductors at once. A US split-phase supply feeds a 240V circuit from two legs, each 120V from neutral and 240V across the two. Interrupting only one leg leaves the device energized at 120V and the switch terminals live — a single-pole switch simply has no place on this circuit. Switches for this class of work carry their voltage and amperage rating on the yoke; the replacement must match both the circuit and its breaker.
The neutral is not part of the job on most of these devices. Standard US guidance routes the two hot conductors to the switch terminals and the ground to the green grounding screw, with neutral left unconnected. Some devices are exceptions — Dimplex’s timer manual lists L1, L2, N, and G terminals and says to connect all four as labeled — so the device’s own diagram is the last word. If you’re choosing hardware for the job, our tested roundup of the best 240V switches narrows down the models worth your money.
The Wiring Sequence, Step by Step
Do the work in this order, and check every step against the diagram that shipped with your switch. This is safety-critical, code-governed work: OSHA’s wiring design requirements cover it, and local code or permit rules can add to them.
- Shut off the circuit at the main breaker panel. Lock or tag the panel so no one flips the breaker back while you work.
- Verify it’s dead. Use a non-contact voltage tester on each conductor, or a multimeter reading 0V between the two hots and between each hot and ground.
- Remove the cover and identify the line conductors (incoming), the load conductors (outgoing), and the ground.
- Set any internal voltage selector first. Dimplex’s manual says to move the selector to the 240-volt position (marked 230 on the switch) before wiring.
- Strip about 1/2 inch of insulation from each conductor. These devices accept solid or stranded copper only.
- Land the conductors. Connect each hot to its labeled terminal — L1 and L2 on standard switches, brass terminals marked X and Y on transfer-switch gear — and terminate ground on the green grounding screw. Tighten firmly; the installation guidance for these devices specifies at least 25 lb-in.
- Replace the cover or insulator. Manufacturer cautions make one thing clear: do not energize the circuit with the terminals exposed.
- Restore power and test. On a split-phase US supply, hot-to-hot should read about 240V, and hot-to-neutral or hot-to-ground about 120V.
When the readings match and the switch kills both legs in the off position, the installation is correct.
These are the terminals you’ll actually meet, in the order they appear on typical 240V switch wiring:
| Terminal | Wire to Connect | Notes |
|---|---|---|
| L1 | First hot conductor (black) | From the breaker;
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