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220 240 Volt Air Compressor Wiring

By Dave Rongey - Summary:

How to Wire a 220 Volt Air Compressor: With a standard 240 volt motor for equipment such as an air compressor there are only two insulated wires for the 220/240 volts and one separate wire for the ground.

Understanding Ground Wires for 220/240 Volt Circuits

Electrical Question: Where should I connect the white neutral wire in the sub panel for my 220 volt air compressor?

  • I added a sub panel to my main fuse box.
  • I have 4 wires going to the sub panel.
  • I’m pretty confident according to your wiring diagram that part is fine.
  • I’m rewiring the dryer from the 3 wire to 4 wire, that’s easy.

My specific question is:

  • I have a 220 volt air compressor that only has three wires.
  • Do I connect the white neutral to the neutral bar, or to the ground bar in the sub panel?

I thought if something bad happened the neutral would be the safer bet, but I’m getting mixed answers from other sources.
Thanks for your help, Brad.

This electrical wiring question came from: Brad, a Handyman from Endicott, New York.

Additional Comments: Awesome.

Dave’s Reply: Thanks for your electrical wiring question Brad.

How to Wire a 220 Volt Air Compressor

Application: Electric Circuit for a 220 Volt Air Compressor.
Skill Level: Intermediate to Advanced – Best installed by a Licensed Electrical Contractor or Certified Electrician.
Tools Required: Basic Electricians Pouch Hand Tools and a Voltage Tester.
Estimated Time: Depends on personal level experience, ability to work with tools and the available access to the air compressor circuit and electrical connection box.
Precaution: Identify the air compressor circuit, turn it OFF and Tag it with a Note before working with the 220 volt air compressor wiring.

Circuit Wiring for a 240 Volt Air Compressor

  • Circuit Size for an Air Compressor
    The circuit size will depend on the size of the air compressor and the horsepower rating of the motor. The air compressor users manual will specify the required power source. A dedicated circuit will be required for most larger air compressors. A dedicated circuit will ensure ample power for the unit and prevent tripping a circuit that is shared with other equipment or tools.
  • 220 Volt Air Compressor Ground Wire
    Brad, I understand your thinking, and a lot of people get confused by this. The fact is that with a standard 240 volt motor for equipment such as an air compressor there are only two insulated wires for the 220/240 volts and one separate wire for the ground.

The Neutral Wire and 220/240 volt Equipment Circuit

  • There is no need for a neutral wire with this type of 220 Volt equipment.
  • Newer 240 volt circuits for kitchen equipment such as ranges and laundry room dryers do require a separate insulated neutral wire and a separate ground wire because these new units have 120 volt control circuits.
  • Such is not true for 220/240 volt air compressors yet.
  • With new control circuits coming out for just about everything, this could change.
  • The ground wire for the air compressor will attach to the separate ground terminal strip that is bonded to the electrical system ground.
  • As with any electrical circuit, when installed properly, the ground wire is the most important wire of the circuit because it will help protect the equipment and the user in the event of a short circuit or electrical fault.

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10 Responses to “220 240 Volt Air Compressor Wiring”
  1. dave may says:

    What size of wire should be used to wire a 240 volt air compressor and what does it look like at the breaker box?

    • Dave Rongey says:

      Hi Dave,
      The size of the wire for your air compressor will depend on the HP horsepower rating of the motor. This information is provided on the air compressor motor, and the instruction manual will describe the circuit size that is required. When this information is identified then the circuit size and wire size may be determined. Please see the Electrical Wire page of the website for the Table which describes the wire sizes and circuit sizes.
      Thanks for sharing your air compressor project with us,

  2. Eric Neufeld says:

    I have a 7.5 HP single phase IR compressor in the garage that I am trying to get power to. Unfortunately, the garage doesn’t have 220v and the general terrain around the garage would require some major expense and creativity to get a line there. I do have an old hot tub hookup on a double 50 amp circuit coming from the house that is unused. My thought was to add a weather tight box with a receptacle at the end of the old hot tub line, and then use a 6/3 industrial cable extension cord to reach to compressor and only plug it in when needed. As I know this is not an ideal solution, would it be an acceptable one?
    Any advice will be appreciated.
    Thank you.

    • Dave Rongey says:

      Hi Eric,
      Converting an unused 220 volt circuit as you are describing is OK as long as the circuit wiring has been identified and relabeled at the panel for the new intended use. The circuit breaker must be resized for the air compressor as well, so be sure to get the amp specs off of the motor label, which will state that the 7.5 hp 220 volt motor will require a 40 amp circuit, or the actual specs. The length of the cord for a portable air compressor should be no more than 20 feet long, and it would be best to locate the receptacle or point of attachment close to the air compressor.
      I hope this helps,

  3. Bob Becker says:

    I have a 4-wire cable with red, black, white and bare copper wires coming from the breaker that are used to power a dryer. Can I use this wire to power a 220 outlet for an air compressor? The outlet has two brass screws and one green. How would this be wired?
    Thanks, Bob

    • Dave Rongey says:

      Hi Bob,
      I understand what you are asking, but lets consider everything involved.
      First, we know that the dryer circuit is typically 240 volt 30 amps.
      But what I don’t know is how large the air compressor is. If the air compressor requires a 30 amp circuit, then you could conceivably install a male plug on the end of the air compressor cord and use the dryer plug. However keep in mind that the outlet for the compressor should be readily accessible, and the cord length should be 12 feet or shorter. With this type of setup you will be able to operate one appliance at a time, either the dryer, or the air compressor, but never together at the same time.
      If you find that the air compressor does not require a 30 amp circuit then you should not use the dryer circuit.
      The best solution is to always install a separate dedicated circuit for the air compressor, this way you can run your appliances independently, have the correct electrical circuit protection and every one will be happy – (we hope!)
      The 30 amp receptacle wiring connections for a dryer can be seen here.
      I hope this helps you,

  4. john says:

    Was looking for a wiring diagram to re-hook up my compressor in my shop at home. I disconnected the wires from the pony panel( with the on /off switch on the side) There is a black and a red wire going into the connection box for the compressor ( 220 30 amp single phase ) Reconnected the ground wire to the compressor box. Now it doesn’t work. The motor was just rebuilt as it had stopped before this time and now I am trying to get it running again. If you can help with a simple wire diagram so I can try and see what I may have done wrong it would be e great help to me.


    • Dave Rongey says:

      Hi John,
      The standard 220 volt wiring for an air compressor includes no polarity for the red and the black wire, so you cannot wire them backwards. The disconnect switch should be a 220 volt 2 pole type for both circuit wires. Green earth ground is bonded throughout at the enclosures and the motor. I will make sure to create a wiring diagram soon.
      I hope this helps you get your air compressor motor working.

  5. Keith says:

    I am wanting to wire my compressor up on a on off switch. I have a heavy duty 30 amp switch. I know how to break contact on 120volt is it the same on 240volt? I tried to do it that way but the compressor will not come on. I have 240volt on both sides of the switch but I believe my problem is where it is regulated on the compressor can you help me out? Thanks for your time.

    • Dave Rongey says:

      Hi Keith,
      Yes, installing a switch to control a compressor is typically done using a 2-pole switch matching the amperage of the circuit, wiring the LINE and LOAD appropriately. As for the compressor not starting I would check to make sure it does not have high head pressure where it is starting too soon, but rather adjust the limit switch so the start pressure is allowed to be lower.


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