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    ceilingfanrepair's Avatar
    ceilingfanrepair Posts: 5,733, Reputation: 109
    Uber Member
    		  
    #1

    Jul 8, 2010, 12:55 PM
    For TK, Stan, etc: Proper way to wire a 240v air compressor
    I'm adding a 60 gallon upright air compressor to my shop. It has a 240v motor. Everything will be brand new from the breaker box, which is right next to the compressor. The motor on the compressor has 240 legs and ground. No neutral, the previous owner used the neuntral as a ground.

    The motor is rated at 3hp and 15 amps.

    1. Would the correct wire and breaker be 12-2 and 20 amps?
    2. What sort of disconnect do I need? I presume I can't run romex straight from the pressure switch into the breaker box.

    I need to do this as cheaply as possible. I have tons of 12-2 and a roll of 12-3. We will want to shut off the compressor when it's not in use, however we can use the breaker if that is the easiest way.

    Thanks guys!
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #2

    Jul 8, 2010, 01:03 PM

    Well, I would not run NM right to the pressure switch. If the panel is that close I would run flex or sealtite.

    You just need two hots and a ground. The previous owner simply used a white wire for the ground. I would use two "hot" colors and a green ground to make it right.

    The breaker will serve perfectly as your means of disconnect.
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #3

    Jul 8, 2010, 02:00 PM

    Stan is right, wiring a machine with NM just rubs us the wrong way.

    I would settle for steel MC cable, or even smurf tube at least.

    You can strip the sheathing and use the wire in something else that will offer more protection.

    You taking out a permit for this?
    ceilingfanrepair's Avatar
    ceilingfanrepair Posts: 5,733, Reputation: 109
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    #4

    Jul 9, 2010, 10:43 AM

    There was an air compressor before there before, and for some reason, when the landlord removed it, he removed everything up to and including the breaker. Pretty sure he did it with romex.

    It's out in the country, and I don't know if the building itself is even legal.. . Never thought about a permit. Don't want to get my landlord in trouble.
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