How Do I Wire a 240-Volt Air Compressor?

Some light duty air compressors can use a 110-volt motor and have handles so they can be moved around, but when a compressor is needed for an entire construction site or workshop, it’s often the size of a refrigerator and not made to move. In large air compressors like that, the motors are 240 volts and must be hardwired into an electrical circuit. The only difference between most 240-volt circuits and one for an air compressor is that the air compressor has no neutral wire.

Things You'll Need

• Screwdriver
• Wire strippers
• Black electrical tape

Instructions

1. Turn off the power to the circuit from which your air compressor will draw power. It’s a 240-volt circuit, probably 20 amps with a 12-gauge cable. The amperage may be different depending on the air compressor, but 20 amps is most common.

2. Locate the terminal blocks on the air compressor. There should be a black, red, and green terminal block. Black and red are hot; green is the ground.

3. Cut the jacket of the cable back and strip each wire by about a half-inch to expose the bare copper.

4. Feed the black and white wires into the black and red terminal blocks and tighten the block screws.

5. Feed the bare ground wire into the ground terminal and tighten that screw.

6. Wrap a length of black electrical tape around the end of the white wire to denote that it’s a hot wire, not a neutral as it normally would be.

7. Replace the back panel of the air compressor.

8. Turn the power back on to the circuit.

Tips & Warnings

• To avoid serious injury, be sure that the power is off to the circuit before doing the work.

References

• TPUB: Air Compressor Wiring Diagram