# Idea for repurposing enclosed refrigeration compressor motor



## ericc (Jul 11, 2019)

I saw a discarded compressor in the yard with a three phase motor. It seems that the enclosed type have the pump integrated with the motor shaft, so they cannot easily be salvaged and repurposed. Can they be used for an RPC, since they don't have to drive anything?


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## markba633csi (Jul 12, 2019)

Good question, I would say probably not if it doesn't have a lot of rotating mass and hefty windings.  The pump section probably supports the rotor too so it can't be disconnected, so it may add noise- also, the bearings are/were designed for refrigerant; with that gone, who knows what will happen?
Wouldn't cost much to try it though, just need a starting capacitor and a momentary switch


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## ericc (Jul 12, 2019)

Hmmm.  That sounds correct.  One would have to rig up separate lubricant.  These totally enclosed compressors are pretty quiet, though.  There would be some rotating mass in a way, due to the pistons going up and down.  Otherwise, just looks like scrap.


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## Latinrascalrg1 (Jul 12, 2019)

If its a fridge compressor from a common refrigerator the compressors can be used to very easily make a few items including a pretty decent relatively quiet portable vacuum pump.  They can also be used as an air compressor which can be connected to a tank if desired.  It wont be suitable for an air hungry application but are useful for lots of air supply needs.


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## benmychree (Jul 12, 2019)

Refrig. compressors rely on returning refrigerant for cooling, if used for any other use, they will likely overheat, and yes, the lubricant also circulates, they have no piston rings, so keeping oil in it could be a problem.   Small hermetic type compressors designed for low pressure refrigerants do make acceptable vacuum pumps, I have used them that way for refrig. work.  Sulfur dioxide compressors can be problematic, the traces of S02 left in the compressor, combined with moisture from the air can create sulfurous acid, tending to cause rusting, and subsequent seizing up of the compressor, this can be countered by passing a little anhydrous ammonia through it to neutralize the sulfur.  Likely one will not run into too much sulfur equipment any more, but it is all interesting.  Years ago, I worked on a lot of ammonia refrigeration here locally.


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## Latinrascalrg1 (Jul 12, 2019)

benmychree said:


> Refrig. compressors rely on returning refrigerant for cooling, if used for any other use, they will likely overheat, and yes, the lubricant also circulates, they have no piston rings, so keeping oil in it could be a problem.



This is very true however when your recycling a free compressor and it only last for a short term of positive use, id call that a win!  So yeah it might eventually burn up but there are some things you can do to help keep it running a bit longer.  For instance you could add a small pc type fan to help control any heat buildup.  The "lubricating" problem can be almost totally resolved by installing an oil catch filter can on the output side for the obvious reason.  You can also add a water filter on the intake side right just before going into the compressor case to help keep the oil from being contaminated by moisture or any other fluid that accumulates in the line.  The amount of oil captured in catch container can be used as a gauge for how much oil you need to add back into the compressor before by measuring what came out then adding 5%-10% more for potential loss in the lines.  You refill the oil thru the intake side usually but there are also different ways to accomplish this including drilling hole in the bottom of the case, welding a threaded bung over the hole just like your cars oil pan drain is setup which im told makes the oil changes a breeze! Of course not all compressors are the same and there are some to be mindful of like the sulfur type Bennychree mentioned but overall I have been pretty happy with the secondary use of various FREE fridge compressors ive used over the years.


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## markba633csi (Jul 12, 2019)

Might be fun to watch it blow up and trip the breakers, maybe black out the neighborhood for a spell
Life is short, make it exciting


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## Latinrascalrg1 (Sep 5, 2019)

markba633csi said:


> Might be fun to watch it blow up and trip the breakers, maybe black out the neighborhood for a spell
> Life is short, make it exciting


Maybe I Guess but ive never had one even come close to that but anything is possible i suppose! 

 With that said i have been using a 1980s model portable whole house dehumidifier compressor motor that i found on the curb as a vacuum pump for about 5 or 6 years now with out any problems with nothing done to modify it.  I had it running for about 6 hours straight last fall to fix a car ac system with a bad Schrader valve.  Outside temps were mid 70s and i had a fan blowing on it and it did get hot to the touch and i was worried it would die before it pulled the needed vac on the system but it did the job i set out to complete and its still working.


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## Flyinfool (Sep 5, 2019)

ericc said:


> I saw a discarded compressor in the yard with a three phase motor. It seems that the enclosed type have the pump integrated with the motor shaft, so they cannot easily be salvaged and repurposed. Can they be used for an RPC, since they don't have to drive anything?



First question, If you have the 3 phase to drive the compressor motor then why do you need to run an RPC (Rotary Phase Converter to make 3PH power)?

Not sure what you mean by they don't have to drive anything, The compressor takes a lot of power to run, and so does a RPC. 

If you are going to try to purpose the motor for something other than an air pump, I would open it up and disconnect the compressor section to remove that load from the motor or there will be no power left for your other application.


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