View Full Version : Wiring up 230 volts to air compressor

12-25-2004, 08:32 PM
I got a new 7 hp. Coleman air compressor and can not find any wiring directions on either the motor or in the owners manual so thought I would ask for a little help on it. The first photo I will post has the compressor specs. The second photo has the specs on the motor. The 3rd photo is where the wires attach at.

From what I can tell from the specs on the motor maybe I should hook up to #1 & #6, if this is correct I could attach some eye terminals to the wires and there is a threaded stud coming off of the number #1 & #6 that I could attach the two hot leads to. Then I would suspect the center wire would hook to the ground green screw does all this sound correct?

12-25-2004, 09:12 PM
There should be some kind of pressure switch that the incoming power should go to first.
It may have a little lever to manually turn it off and on.
The picture you show of the connection of the motor should have the wires going over to the pressure switch.

12-25-2004, 09:29 PM
The power supply cord goes to the motor on this compressor, then there is a two wire cord coming off of the motor that goes to the pressure switch. You can see these two wires in the photo of the wiring of the motor, They are attached to terminal on the #1 and the #6 connectors.

12-25-2004, 09:51 PM
All the ones I have ever hooked up the incoming power goes to the pressure switch first. Your's may be different.

Here is a website I looked at but did not see your model #


This may not be the particular site you need though.

12-25-2004, 10:13 PM
Ok, what read in the OM is that if the unit isnt supplied with a cord it needs to be wired to the pressure switch first so ignore any of my previous advice. Its on page 12 of your manual.

12-25-2004, 10:17 PM
The model number is ML7006016 The switch has two wires running from it a black wire and a white wire, black wire goes to the #1 terminal and the white wire goes to the #6 terminal. There is a double lug with no wires going to it that is numbered #3. The number 6 lug also has an extra lug at it with no wire hooked to it.

12-25-2004, 10:24 PM
I deleted my first reply as I was full of it and re read your post. It must be wired to the switch first as per page 12 of your manual. Units shipped without cords are customer supplied. If you use solid wire like romex make eyes. But, it should really have a cord instead of solid wire, then use crimp eyes, I use yellow as they are heavier than blue. They allow number 12 wire to 50 ft and dont spec the breaker, but, I would run a 30 as these often trip a 20. The wire must be 125% of the FLA which is 15 on this unit so 12 qualifies as it is good for 20, it has its own internal thermal protection to protect the incoming wire so you can over breaker it at 30 no problem. You have a 3 hp comp, ignore the factory claims.

12-25-2004, 10:53 PM
OK, I went back and looked on page 12 of the manual and do see now where it says it must be wired to the pressure switch. I went back out to my cold cold shop and looked at the pressure switch and do see where the cord would come up through the bottom back side of it. I took the cover off of the pressure switch and looked at it. There is two empty lugs inside for the two hot wires to connect to. There is also two separate green screws under the switch cover I am supposing that the third wire or the common wire would attach to one of these green screw is this correct?

12-25-2004, 11:43 PM
Yes, the ground must be hooked to the frame of the machine, one of thse screws is correct. But, this is not a common wire, it is a ground and goes to the ground bar in the panel if it is a subfed panel, like your garage panel is fed from your house panel correct? Hook it the same place the rest of the ground wires from any other circuits go.

12-26-2004, 12:11 AM
Thanks Sberry, & Scott778. I think I will be OK on it now. Sberry I got my terminallogy off on the third wire as it is my ground wire.

Sberry where do you find the information at that this is a 3 horse compressor? I don't doubt your word on it, I figured it might have been rated a little high, but was hoping it would be up around a 5 h.p. My last air compressor (different brand) was over rated and the company that made them was later involved in a lawsuit over that. They just recently was giving out rebates to customers that had purchased one of their compressors.

Thanks again for the help.

12-26-2004, 12:26 AM
I looked up the model from the link Scott posted. It says 15 run amps. It also lists 12 cfm @40 and 10@ 90 which means the pump ist extremely effecient although I am more familiar with 2 stage units than singles. With 2 stage the basic figure is 4 cfm per hp. New motors of this type are about 5 amps per hp, so 15 divided by 5 = 3 These are aproximations and not exact wattage/conversion formulas, just rules of thumb probably within 10% or so but close enough for this discussion. A basic rule is you cant get something for nothing, so it uses 15 amps, can only be making so much power. The allowances for advertising eave a lot to be desired, if you notice it says 7 hp peak, well, basically it saying when this motor is starting under load it pulls enough electric to be equivilent to 7 hp,, (kind of a simple explanation) The manafactures all got together and lobbied to help themselves with allowing this kind of labeling. Great example is a wet/dry vaccuum, and some small comps, they say 5 peak hp on the box yet they plug into a 120v circuit which will in reality make 1 1/2 hp at best.

12-26-2004, 12:51 AM
The allowances for advertising eave a lot to be desired, if you notice it says 7 hp peak, well, basically it saying when this motor is starting under load it pulls enough electric to be equivilent to 7 hp,, (kind of a simple explanation) The manafactures all got together and lobbied to help themselves with allowing this kind of labeling.

Dang fuzzy math is what it is. Must be the same guy that does their taxes also makes the HP labels. Here's a short and sweet site that substantiates what you just said. Also notice they say 4 to 5 cfm per horse @100psi. If a compressor then delivers around 10 cfm at 90psi, well, the math says its a heavy 2hp or short 3hp. Sad.

I guess the main thing when shopping for compressors now days is to look at the air out put. HP ratings mean little.


12-26-2004, 09:38 AM
I will just have to be happy with the added air volume that I will have with this compressor, and hopfully it will be a lot quieter then my other one which was an oiless compressor. That sucker would pretty near run me out of the shop.

I sold a better compressor to get some of the money for the oiless compressor, the one I sold was either a 1 or 1 1/2 horsepower Sears single stage portable air compressor. It was far less noisy, but just didn't have the air volume I needed. I had the sears for about 10 years. The guy I sold it to is still very happy with it and has used it to roof a few houses with.

Recently I got a plasma cutter and the oiless 5 h.p aircompressor was having to run pretty much constantly to keep up with it. Put the added problem of having to deal with the noise it was almost enough to keep me from using the plasma cutter.

02-21-2005, 03:31 AM
I was checking thru the old posts and came upon yours about AIR. So if anyone else is looking for a GREAT Air Source other then the Major Warehouse types check this out.
www.eatoncompressor.com . I needed something to paint with and to run my Hypertherm
1100 plasma with consistent out put. So Purchased the 80Gallon V2 @ 19 1/2 Cfm true output.
Had them put in 2 outlets on the tank and the magnetic starter on the right side. easy access for my power hook up.....$999.00 plus shipping to the West Coast... I Still purchased a better compressor then the box stores could ever provide.. Check it out you will be most pleased.. And they are nice Folks to talk with. Now I have true confidence while running the Plasma.
Mortch ( This is not an Add this is a Fact)