air conditioner pump use as compressor

[darryl]

I was given part of an air conditioner unit a few weeks ago. This is the outside unit that sits on a slab, with the wrap-around cooling coils and top-mounted fan. I was told that the compressor works, so now I want to convert it into an air compressor. Chances are it has lots of power, unlike a refrigerator compressor, so it should be perfectly able to give shop air at a reasonable speed for my home shop. Anybody ever do this? I've used the 'fridge compressors like this before and it works- just slowly. This should be better, and reasonably quiet as well.

I don't know why it was 'scrapped'- I think it was because someone had tried to steal it but got scared off after they had 'hand-fisted' the copper lines apart. The owner subsequently moved and took this with him. Without the inside part it's useless, so it became mine.

At any rate, it's powered by 220vac which is fine by me as that's the only power I have available now. My breaker box is full and no more circuits can be added. I hope the breaker for this circuit, and the wire size feeding the outlet are rated high enough to handle the motor.

Being what I'd call a 'newer type unit', the refrigerant should be a safer type, and there should be no pcbs in the oil. I don't anticipate any problems with it smelling, but I really don't know. I don't want to contaminate the air in my house with an unsafe 'compressor smell'.

Comments?

[Highpower]

Those types of compressors rely on the circulation of oil & refrigerant in the line set to cool the compressor as it's running. It won't run very long without it I'm afraid.

[Sparky_NY]

Those types of compressors rely on the circulation of oil & refrigerant in the line set to cool the compressor as it's running. It won't run very long without it I'm afraid.

True, also the freon cools the compressor somewhat also. The oil in older R22 systems was just mineral oil, the newer R410 is POE oil, neither is nasty stuff. If its a newer R410 compressor, they ran at MUCH higher pressures than R22 did but lower volume. If you try it you will want a good oil separator at the outlet, and recycle that oil back to the inlet (slowly) when it fills up some. There is a quite a bit of oil in the compressor, a quart or more, not much circulates through the lines on a AC system but it does circulate with the freon somewhat. That compressor is intended to run nonstop 24/7 so you might get away with it for your intermittent use.

[RB211]

Thats what my piece of junk compressor is. Been that way forever.

[J Tiers]

Newer refrigeration compressors need the oil in the freon.

Older ones, with an oil sump, are fine. Work indefinitely so long as there is enough oil

[Andre3127]

Those types of compressors rely on the circulation of oil & refrigerant in the line set to cool the compressor as it's running. It won't run very long without it I'm afraid.

Wrong.

I have used a centrifugal style r22 refrigerant pump from a dehumidifier for a year now on my silent compressor. It does oil the air and you have to feed it some oil once and awhile. Make sure the oil has a very high flash point, just in case.... But the amount of oil in the air isn't much more than a worn out piston type.

I have another pump spare when I eventually blow it up (from over use), but I don't think I'll need it in the near future. I used the silent compressor today, actually.



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[MattiJ]

Wrong.

I have used a centrifugal style r22 refrigerant pump from a dehumidifier for a year now on my silent compressor. It does oil the air and you have to feed it some oil once and awhile. Make sure the oil has a very high flash point, just in case.... But the amount of oil in the air isn't much more than a worn out piston type.

I have another pump spare when I eventually blow it up (from over use), but I don't think I'll need it in the near future. I used the silent compressor today, actually.



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Centrifugal? Not rotary or scroll?

In OP's case I would try to change the oil to normal air breathing compressor oil.
And you have a problem if the compressor happens to be one of the newer pm synchronous motor/ inverter combos. Those wont run without inverter electronics and to trick the inverter board to work might turn out really tricky.

[JoeLee]

You won't get much volume out of it. When I was a kid the guy down the street made an air compressor out of one. It took almost a half hour to get enough pressure in a 50 gal propane tank to fill my bicycle tires.

JL....................

[darryl]

As far as I know, compressors like that recirculate their own oil- I doubt that much oil at all circulates through the system. It would seem to be a hindrance to cooling and probably difficult to keep from collecting just where you don't want it.

There was no oil in the lines that I cut to remove it from the base, and no oil in the tank-like thing that's inline with one of the pipes. No evidence of oil in the condenser, at least none leaking out regardless of the angle I held it at.

Now I have to determine if the capacitor in there was meant for the compressor or for the fan motor.

[darryl]

As far as changing the oil, I can see no way to do that aside from turning the unit on its side with one of the copper tubes at the low point. Both tubes are on the same side of the unit, so either one might pour out oil. There's no way of knowing if all the oil can be extracted and the exact amount of a replacement oil determined.

There was no circuitry on the thing at all, just a point where the ac line came in and went to the relay with all it's terminals. I don't know if the fan motor is 220 or whether it gets 110 by means of a neutral wire. I'll have to decypher the wiring.

[winchman]

I used the compressor from an old refrigerator as a vacuum pump for several years. The electrical connection was at the top, so I put the compressor in a tub of water to keep it cool. There was only a tiny bit of oil coming out the discharge side, but I'd put a little oil in the vacuum line each time I used it.

It worked fine for evacuating the DIY auto AC systems I installed back in the '70s.

[Tim Aldrich]

Go look up Halligan142 on YouTube. He made a compressor out of a refrigerant pump. His day job is a heating/air conditioning tech so he knows what he's doing.

[Planeman41]

Back in the mid 1950s when I was a teenager building model airplanes I rigged up a refrigerator compressor to operate an air brush. As it had a starting coil, I had two switches side by side to turn it on, one for the starting coil, the other for running. I flipped both switches on together to start the compressor and immediately switched off the starting coil. Worked like a charm!

[Andre3127]

Centrifugal? Not rotary or scroll?

In OP's case I would try to change the oil to normal air breathing compressor oil.
And you have a problem if the compressor happens to be one of the newer pm synchronous motor/ inverter combos. Those wont run without inverter electronics and to trick the inverter board to work might turn out really tricky.

I'm not sure what it's called exactly... It's shaped like a tower, and not a bubble like a fridge compressor.

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[A.K. Boomer]

Years ago one of my bro's threw a GM style car comprendo on an old lawnmower base and hooked a motor to it,

it was a duel piston self contained lower end so had it's own oil res.

we used that thing for years - could not kill it, it had no tank - was just direct air for pumping up tires and stuff, and you could use it as an air nozzle some as when you stopped the end with it's shut off valve it would labor and build up quite a bit of pressure, you also had to have that closed to fill tires - had two lines one with the shut off and the other with the tire filler end,

thing was very funky and made a funny sound when working but my Dad loved it and was actually proud of it cuz my bro threw it together as a kid.