Definite Purpose Motor Starter to Air Compressor?

[ChuckD]

Hi everyone,
I bought a used 5hp air compressor that came with a "Definite Purpose Motor Starter"("DPMS"). The tank has a pressure switch but the motor is not wired to it. The pressure switch has 2 screws in and two screws for the motor.
I could not find a model # on the "DPMS", I did find 20/25/30 A, on it.
Could someone explain to me how a "DPMS" works and how would a guy go about hooking this thing up? It is a single phase 220V, 20A. motor.

Thanks for the help,

[ChuckD]

http://www.freeimagehosting.net/uploads/th.7c0fdfdca9.jpg (http://www.freeimagehosting.net/image.php?7c0fdfdca9.jpg)
heres a pic of the guts. the white wires at the top are coming from a fuse box(power) the white and black at bottom are going to the motor, the green wires are coming from the pressure switch. my question is where do I connect the green wires for the pressure switch.
thanks again
Chuck

[tfi racing]

Do you see the small spade terminals at the top of the starter in the back?They should be the coil terminals,its hard to see in the photo.

[buening]

That is basically a contactor and coil, which are commonly called a Magnetic Starter box. The top portion (which is the coil) has a sticker on it. Somewhere it should state what voltage the coil is. If the coil is indeed a 240V, then the two gray wires at the top are the two 120V legs from the breaker box. The two spade terminals are the terminals to the coil. Do you know if your compressor has a low oil shutoff or an electric drain wired to the box? This can complicate things, but my compressor has both.

I had issues with my compressor when I bought it used. The previous owner installed a 120V coil in a 240V contactor, which blew the coil. He then tried rewiring the box and really screwed stuff up. My experience is simply rewiring my starter box and hooking up the 240V to the box. I am not an electrician ;)

[buening]

I'll let the more experience person help with the wiring, but you will need to locate the spade terminals on the contactor coil (may be labeled A1 and A2 or C1 and C2), and the 2 or 3 terminals on the side of the overload block. They may be labeled C, NC, NO or no labeling at all.

I believe on my compressor, one wire comes from the pressure switch and attaches to the L1 post. The other wire from the pressure switch attaches to the A1/C1 post on the coil (which is likely the left spade terminal). Then there is a wire from the A2/C2 spade terminal to the overload block. From the overload block comes a wire to the L2 post. One wire comes from the T1 post and goes to the compressor motor. There is a heater (fuse-like) installed on T2, but after the heater should be the wire going to the other leg of the compressor motor. Again, this is for my 240V coil and 240V single phase compressor motor. Please wait for a more knowledgeable electrician to confirm before wiring!

After looking at your picture again, I don't see a heater installed on the T1 post. Could this be a 120V coil?

There is a wiring diagram at the bottom of this PDF (use the 120/240 single phase diagram) for reference.

http://www.jackssmallengines.com/campbell_index/Air%20Compressors/HS/H%20S%20Service%20Information/Mag%20Starter%20Wiring%20Inst..pdf

[ChuckD]

thanks buening & tfi
I was told it is 220V unit, but I'll look it over again and see what I can find. I've been busy with work and have not been in the shop all week
I'll look at the spade terminals and see if there is anything there and as far as the compressor having a low oil shutoff or electric drain, I don't know. I got the thing in pieces with a bunch of other stuff and have cobbled it together with the compressor stuff I'm aware of(so much for great deals, eh?)
I'll post my findings soon
thanks again folks,
I have something to start with now