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wiring new air compressor
- Thread starter toddjg
- Start date
porcupine73
Well-known member
The two black wires are most likely the two hots. The white may be a neutral and the green may be a ground. Many 220VAC loads do not need the neutral; that's usually there only if it uses 110VAC for its control power and 220VAC for the load.
So provided the colors are wired to convention, if I were doing this, I would hook black from compressor to one of the blacks in supply line. I would connect the red from the compressor to the other black in the supply line. I would connect the green as the ground for the compressor. I would put a cap on and not use the white/neutral unless the compressor has a connection for it, which it most likely does not.
So provided the colors are wired to convention, if I were doing this, I would hook black from compressor to one of the blacks in supply line. I would connect the red from the compressor to the other black in the supply line. I would connect the green as the ground for the compressor. I would put a cap on and not use the white/neutral unless the compressor has a connection for it, which it most likely does not.
I recently went through the 3 vs.4 wire question while wiring up my air-compressor. My local home depot left alot to be desired in terms of electrical professionals on staff(I'm not one either!). When inquiring about a 4 wire vs. 3 wire I got varied answers and all over the map and most said by "code" had to run a 4 wire set up and had to hook up all 4 wires to the compressor. At the end of the day, choose to purchase a 4 wire 8 gauge and ran 20 ft cable in flex conduit to my 5hp 21amp compressor(see reasons below). Also installed a 50amp breaker as starting the electric motor pulls a higher amp draw before settling down to its run state of 21 amps which is what my electric motor is rated. If running a length of cable from your electrical panel to air-compressor across the garage, make sure you use a heavy enough gauge. For shorter runs I could have used a 10 gauge wire. Since I was running 20-25 ft went with a 8 gauge wire.
I hooked up the following for my air-compressor install:
Red-hot, black-hot, green-ground. No white-neutral was used).
Within my compressor switch box located on the unit itself, I hooked up 1 hot wire-black to the shut off electrical bus-bar, 1-hot wire-red to the electric motor wire, and 1 wire-green to chassis ground. Again, no white-neutral used in my set up.
Purchased a 4 wire cable vs. 3 wire so that in the future if I wanted to hook up 1-hot wire and 1-neutral-white from my extension cable that would give me 120v for adding a lighting fixture near compressor, coffee maker, whatever. Figured I'm going to run and install the feeder cable myself one time, might as well run a 4 wire and be done. Also incorporated locking twist lock 50amp male/female connectors so that I could disconnect the power at the air-compressor location at any time and plug in a 220v welder some day, then switch back when air is needed,etc.
If interested in some pictures, I can start a new thread regarding my compressor and air-line install.
I hooked up the following for my air-compressor install:
Red-hot, black-hot, green-ground. No white-neutral was used).
Within my compressor switch box located on the unit itself, I hooked up 1 hot wire-black to the shut off electrical bus-bar, 1-hot wire-red to the electric motor wire, and 1 wire-green to chassis ground. Again, no white-neutral used in my set up.
Purchased a 4 wire cable vs. 3 wire so that in the future if I wanted to hook up 1-hot wire and 1-neutral-white from my extension cable that would give me 120v for adding a lighting fixture near compressor, coffee maker, whatever. Figured I'm going to run and install the feeder cable myself one time, might as well run a 4 wire and be done. Also incorporated locking twist lock 50amp male/female connectors so that I could disconnect the power at the air-compressor location at any time and plug in a 220v welder some day, then switch back when air is needed,etc.
If interested in some pictures, I can start a new thread regarding my compressor and air-line install.
Last edited:
climbabout
Well-known member
- Joined
- Oct 10, 2011
- Messages
- 58
Just trace that 220v line back to your panel and find the breaker that powers it. It should have the 2 black wires attached to it. When running conduit for 220v, whether it be EMT, PVC, Rigid Steel, or some kind of flex, it would be common practice for the electrician/installer to use 2 black wires for the 2 hots since there is really no need to distinguish between them. If this was wired with romex or bx cable which of course already has the wires in it, then you would see a black/red/white and bare ground.
Tim
Tim
the 220 line that is there now is wired into an outlet the 2 blacks goto the power the white goes to the ground the green is ayyached to the outlet box its really just been pulled through the box not screwed in.
I was going to wire the 2 blacks power white for ground and attach green to frame.
Or wire in a plug and outlet.
I was going to wire the 2 blacks power white for ground and attach green to frame.
Or wire in a plug and outlet.
What's on the compressor? Does it have a cord and plug or is it meant to be hardwired? If the compressor has a white wire (assuming USA color codes) it is meant to be wired to the neutral buss in the panel. It is not a ground wire. That's what the green or bare conductor is used for. The ground wire should go back to a ground buss in the panel or may be screwed to the panel case. The two hot conductors go to the load side of the breaker that's feeding that circuit. If there is no white wire in the compressor and there is one at the outlet box, cap it off and don't use it.
porcupine73
Well-known member
In the panel where this circuit originates, are the neutral and ground bars bonded? If they're separate (which they should be unless this is the main panel the utility supply comes into), if I were using the white wire as a ground, I would make sure the white is colored green like with paint or a sharpie marker, and make sure it is connected to the ground bar in the panel and colored green on that end too. To make it clear it is being used as a ground and not a neutral.