Compressor question

Hey guys,

I recently acquired a free air compressor and I'm trying to find information on the motor.  It says it's a dual voltage motor but I can't figure out how it's supposed to be wired if I want 115V.  I don't have 220V in the garage so I would like to swap it over.









I'm hoping that I don't have to pull the whole back half off the motor.

You probably need to remove the wires so you can lift that plastic shield and reconfigure the winding's connections.
You certainly don't need to remove the bell.

2hp is 1500W, so be sure the wire gauge of the cord is up to carrying the doubled amperage you need to run it at 120V.

By using ohm's law we know IV/R 1500W @ 120V is approximately 12A.
I would probably play it safe and use a 14Ga. cord.

Here is a video explaining the different winding configurations for 240 V 120V
Jeremy is really good at simplifying electric circuits.
https://youtu.be/3llc68VvzsY

And another from Matthias in Canada:. https://youtu.be/hHuYEDDArYQ

Thanks!  I knew the coils needed to be changed from series to parallel, I just haven't ever done it on an AC motor.  My background is Electrical Engineering, but I specialized in Electromagnetics so I deal with analog, digital and RF circuits, but not so much with the high power AC devices.

With any luck there's a diagram on the back of that plastic cover so I don't have to ohm out each coil.

I've always seen a sticker on the inside of the metal cover plate but perhaps it's molded into the insulator.

It really isn't too troublesome to ohm out a few wires, but as noted 'polarity' matters in order to keep things in phase.

I pulled the plate of the motor last night and there's nothing on it unfortunately.

I just got the 12 gauge extension cord to rewire it so I'm going to dig into it today.

Thanks!

Looks like I get to enjoy this..



The plate shown in my earlier post is attached to the inside of the back panel.  I popped the panel off and can see the windings zip tied up top.

My son woke up from his nap early so I didn't have a chance to meter them out yet.

I may take some time to solder a bleed resistor across the start capacitor while I'm in there.

12A not 12Ga.  You could have run it on a 16Ga.. cord...  

The metal cover plate you have hanging by one screw in the prior picture says 12A, so it must have come wired 120V
But the line 1 & 2 are reversed from what is shown (If the plug is wired correctly)


I'm astounded that the windings aren't set up with jumper(s) where you can just swap some wires around in the terminal block.
That gob of electrical tape makes it seem someone's been in there.

But it seems you've got the bell off now,  so..,...  

I know it only draws 12A, the cord it's on is 16GA, i prefer to over build it.  I also went with a longer cord than is on it now.

Once I can get back out there I'm going to pull the front out and check the bearings and look for scoring.  Someone has been in it before, the bearings have been replaced with sealed ones.

Took the motor completely apart.  It's been rewired to a single voltage motor.  There are only two windings inside, the main winding and the start winding.

Looks like I'm on the hunt for a dual voltage motor.

It's usually just a single (center tapped) run winding.
But I'm not there looking in it, like you.

So you're saying there are only four connections, not six?
These old Craftsman compressors must have been everywhere back in the '70's!


If you're looking for a quick and dirty fan cooled 2hp 3450 rpm motor what shaft size do you need?

Correct, there's only 4 connections. 1 main coil and the start coil.

I have to find my calipers lol, then I'll be able to measure the shaft diameter. It looks like 5/8"

Update!

Replaced the motor with a 2hp dual voltage from Northern Tool.  Ironton

Compressor runs and fully pumps.   I did notice that it doesn't appear to have a check valve or if it does is has failed.

Once the compressor kicks off the unloader valve opens and drains the tank back to the kick in pressure.

The motor struggles but does start which says to me the head is still under pressure.

Going to take that section apart next.



I was discussing this compressor with my coworker when he mentioned he had one that I could have.  It had been sitting in his yard for roughly 18 years, so naturally I grabbed it.





This one is much newer than the craftsman.  It's a Puma PK-5020.  The date on the tank is 2002.  All that this one needed was a new circuit breaker on the motor.  Unfortunately or fortunately I had already ordered the motor for the craftsman.

Now I have 2 20 gallon air compressors.

You are knee deep in compressors!  

You have 1 compressor and 2 - 20 gallon tanks LOL
On most compressors the check valve is at the end of the air tube before it goes into the tank.
If the tubes and tank opening are the same size you may be able to take the one from the Puma unit to use on the Craftsman?

I think I have a link for compressor parts if you need it,if it is still good as I have not used it in years.

I used a 30 gallon Craftsman dual voltage (on the higher volts) for a while till I did not check the oil and it now has a knock.
I did look into a new compressor unit to bolt to my tank but the more I got thinking it was really to small for the body work I had to do.

I found on Ebay a used SnapOn shop compressor that said had work done to it before being disconnected.
When I went to start it I found the starter box had the contacts welded closed!
This was from a bad check valve like yours and tried to start with air psi on the pistons.
I also found the heads were loose on start up but the pistons & walls looked great.

Replaced the check valve, the reed valves in the heads as I replaced the head gaskets & starter contacts.
I bought for $1000, have about $200 in to it, the unit new goes for $5000 and is way more than I will ever need.
Hooked to my home made air cooler / drier and 5 air hose drops around my garage it is better than most shops have LOL

Dave ----

Now I really am knee deep in compressors! I put my bullnose to work on the way home and snagged this :





The compressor head has been change to some unknown unit and the motor is only 1/2hp 110V 1725rpm.

The motor was seized when I got it, but I was able to free it up and determined that the front bearing is toast.  I've got some replacement bearings on order.  This thing has been kludge together. The motor has a v belt pulley, but the compressor is a poly groove, they just had the v belt riding on the groove.

I did not pay the full asking price.

Worst case I pull the motor off the craftsman and use that, but it's a 3450rpm so I have to make sure that the pulley is small enough. Or I use this as an additional storage tank. Haven't decided yet. If I use it as a storage tank, I'll have to limit the craftsman to 125psi instead of the 150 it currently is set to.

Chris - Why would you have to limit the Craftsman to 125 if you use this tank and storage?  This one is rated at 150.

Does the compressor have RPM ratings on it?  And what size is its pulley?

I would derate for safety. The tank is rated to 150, but I think the unit when new was only run at 125, I'll have to look it up again.

The compressor head has no markings from what I can remember, but I'll take a closer look. It's pulley is 10" diameter.

I looked up the compressor and the unit when new was saying 125psi max



I had another look at the pump head.  There are some marking very poorly embossed in the casting, but nothing I can make out.  I thought one might have been a Campbell Hausfeld logo, but it's not from what I've been able to locate on the net.

I don't expect the thing to fill quickly, the motor is only 1/2hp so I suspect the pump head is from some other 20 gallon unit that they took apart.

If you are going to use both tanks as storage then you have to limit the PSI to the lowest safety valve and that would most likely be on the 125 PSI set up.

Also note the safety should release at or more CFM than the pump can put out.
If the pump puts out say 20 CFM and the safety only 15 CFM the tank will still keep taking on PSI till it blows up and that is not fun when it happens!

I dont think I would use the "oil  less" pump to fill the 60 gallon tank as I think the pump will burn up in short order. I would use the pump on the 60 gallon take as it is oil type just set it up with the right belt set up.

Being you think the set up was put together from parts because of the belt set up maybe that pump can run at the high motor RPM of the smaller tank setup?

I have a few air compressor part sites saved some were if you need them let me know and I will try and find them.
Dave ----