Need Help Wiring old Air Compressor

This might be better over at alt.home.repair .... but anyway.... I would install a disconnect box somewhere near that appliance outlet and run a flexible conduit with all the proper fittings to your compressor. I can't tell how far the outlet is from the compressor...It should be pretty close. Just go to the hardware store and they should be able to help you. If you don't fell comfortable with all this you might just hire an electrician to do this for you. Please do not use that outlet...the rusty screws are not safe.....Ross

Thanks Ross..I will post on the other group as well. The outlet is right above the compressor just didn't put it in the shot. I can replace the screws or just switch out the outlet box for something more suitable to my situation. I just felt uncomfortable becasue I wasn't sure of the wiring to the motor and that is why I placed the topic here.

Thomas

Wow someone who posts a question with the information provided.

First you realize that the 50 amps is WAY over the 15 amp draw of the compressor? Not code to connect directly. Your going to need to either fuse down the wiring in the panel, new 20 2 pole breaker or your going to have to remove the plug you have install a fused disconnect and use that for the protection of the motor. I prefer fuses for motors, just a simple pull out disconnect would do. A manual motor starter would be better.

The pressure switch needs one of the lines brought to and through it. then to the motor. The other hot just lands on terminal 2. This way the pressure switch controls the on and off. You did not show the other end of the cord on the pressure switch so,,,, no joy there.

I would use #12 stranded wire and "push-on terminals" some would use ring terminals inside the motor. Your compressor your choice. The ground wire would land under the cover screw or ground screw if available. 12-3 SO cord would be a good choice, SJ if you want to save a tad of cash.

Have fun, hope I helped not hindered.

SQ left you some great additional info and I wanted to add....good post with lots of information....Ross

SQLit, Thanks for the info, I have a few clarifications.

The motor is thermally protected and has a red button to reset the motor when it has a problem. Do I still need this additional protection...is this internal circuit breaker not safe enough? I realize 50 amps is too big...I was just trying to simply use the outlet because it was already there. I felt it would be easy to find a plug that fits the outlet and run a short cord to the pressure switch. This compressor will not be left plugged in and will only be used when I am actively working on a project. Although, adding a fused disconnect sounds easy and I could then go with a 20 amp 240V outlet with matching plug..right?

The first image is of the pressure switch with the cord attached that is coming from the motor and the second image is of the same cord but the other end which is attached to the motor at positions 2 and 4 using push-on terminals. The wires are simply black and white and you will notice that there is an empty hole next to the cord going into the pressure switch this is where the original plug cord was but is now missing.

Thanks for you assistance Thomas

You need a ground, which you don't have at present. And the 50 amp is oversized for the motor and connecting wiring, regardless of the motor's thermal protection.

...is this

Yes.

Red----Pressureswitch-----motor terminal 2

Black---------------------motor terminal 4

Ground--------------------motor frame

Re-identify the white as ground by wrapping it with green tape, at both the service panel and the outlet ends. Replace the existing receptacle with one rated for 20A, 230 V. Wire the motor with SJ to a mating

Ed

Ed,

Thank you for the information. I will utilize a 20amp fused disconnect and go with 20amp 240V outlet and plug using 12-3 wire. I will attach the black and red to the line side at the pressure switch and the white I will attach to the clip/screw that holds the cover to the pressure switch. I confirmed continuity between the motor chasis and the clip at the pressure switch so they are common.

My confusion was that I did not know that 240V circuits did not need a neutral for the return path of electrons but rather the hot leads traded off acting as one. I kept asking my self how/where to attach the white wire because it was obvious at the pressure switch that there were only two terminals and both had to be hot in order to get the

Thomas

I would guess that it is exactly as you surmised - the neutral (white) was used as ground. Your description of how you'll wire it sounds good.

Ed