Central A/C Compressor to "Silent air compressor"?

[Markfothebeast]

I read about refrigerator and freezer compressors being transformed in to "silent air compressors". Yesterday I managed to grab a home central air compressor and I'd like to attempt this if it is possible.

The label on it identifies it as a "Rechi Precision" brand, 115v, R22 (refrigerant I assume), model 44R281A. I looked in to different types of AC compressor to air compressor mods over the years and have no experience with AC systems and refrigerants (I never use AC).

The automotive AC pump to air compressor DIY got me interested as well. I recall reading that the pump must be the internally oiled type to convert to an air compressor. Which I'm assuming that certain types of refrigerants contain oils that lubricate the compressor. Does this apply to electric AC pumps? I'm not quite sure if this would be the proper type to run as an air compressor.

Is there a formula to determine PSI and flow based on the chart below? (model circled, tables listed on bottom). I'd like to see some photos and get some input if others have completed this successfully.

 

[Markfothebeast]

Here it is. What's the blue wire? Foreign wire color for ground maybe? It says 115v. 240v legs are typically red & black. Or perhaps it is a second 115v wire for another function I'm not aware of.

 

[Lelandwelds]

Weird photo angle but that looks huge! Are you sure the plate doesnt say 3 phase and use a VFD? Most people use a tiny frig pump for those builds.

 

[Markfothebeast]

There's a measurement.

 

[Markfothebeast]

I determined that the blue wire is for a start capacitor.

 

[pop pop]

You may find cooling the motor is an issue for compressing air. Just guessing here.

 

[just a noob]

I think the issue you'll run in to is the oil. Usually it absorbs moisture out of the air and turns acidic, and that ruins the compressor.

 

[Dagny]

won't last long be careful

 

[monkeyspanners]

Thats a rotary style compressor, the inlet goes straight into the cylinder via the accumulator on the side, the compressor body acts as a muffler/ oil separator for the refrigerant and dischages out the pipe on the top.
I would be wary of the possibility of dieseling if used to pump air. In a normal air con system the compressor would easily be capable of a 350psi discharge pressure and in a fault condition you could probably double that.

 

[American Locomotive]

The blue wire is for a run capacitor, not a start capacitor. That is not a "central air" compressor. That is out of a 11,000 BTU window unit or minisplit. It's a roughly 1HP compressor, and would only be good for about 3 CFM tops.

As mentioned, that is a rotary compressor. Rotary compressors pass a lot of oil due to their construction. The pumping element is actually at the bottom and more or less sits in an oil bath. You would need a very good oil seperator on the discharge capable of recycling all the oil back into the intake.

Traditional reciprocating refrigeration compressors (the oval looking ones) pass far less oil out the discharge.

 

[Markfothebeast]

Thats a rotary style compressor, the inlet goes straight into the cylinder via the accumulator on the side, the compressor body acts as a muffler/ oil separator for the refrigerant and dischages out the pipe on the top.
I would be wary of the possibility of dieseling if used to pump air. In a normal air con system the compressor would easily be capable of a 350psi discharge pressure and in a fault condition you could probably double that.

Thanks! I thought about the combustion/dieseling possibility. But there's compressor oil for that reason. How many CFMs do think something like this would put out directly from the line in open air?

 

[Richard Cranium]

I am not the a.p. But good to know. Thanks guys.

 

[American Locomotive]

Thanks! I thought about the combustion/dieseling possibility. But there's compressor oil for that reason. How many CFMs do think something like this would put out directly from the line in open air?

Read my post above.

 

[Markfothebeast]

Re: Central A/C Compressor to "Silent air compressor"?

I did a little research on the rotary compressors. It looks like the issue here would be keeping the oil inside the compressor. It appears to have a chamber for oil in the bottom of the sealed housing. I'd like to know how much oil evacuates the bottom before it needs to be refilled. I could put an oil separator on the line and keep an eye on it.

The accumulator is intended to separate fluids while the gases/air pass through in to the rotary chamber. The chamber is intended to compress low pressure, low temperature refrigerant so I don't see filtered air being a problem. I wonder what the duty cycle is?

I pulled this out of a scrap pile so I'll give it a shot. I've got the proper oil on hand as well.

 

[American Locomotive]

The accumulator is designed to allow liquid refrigerate time to boil off before getting sucked into the compressor. Most rotary compressors will emit a constant fine mist of oil while running.

 

[kctyphoon]

 

[Markfothebeast]

Interesting. I didn't finish the video but I think that's a different monster over this rotary unit. Also, I saw the use of 10W40 which is not terrible but can pose a risk of turning itself in to a diesel oil style engine under enough compression!