Visual Inspection of Compressors

[Wickfut]

Hi, I want to build a small tabletop refrigeration experimental rig.

I intend to make a condenser and evaporator out of copper tube and use a simple capillary tube as my metering device. Maybe a TXV further down the line.

I am a degree qualified electrical engineer and have no problem with the wiring of the compressor and identifying faulty motor windings, so I guess my main question is how do I identify a good/suitable compressor by sight and simple inspection? What do I look for?

There's a guy in my city that sells used refrigerator parts, he literally has hundreds of compressors in piles in his yard. Without actually wiring one up and running it and listening for obvious rattles and strange noises, connecting gauges to measure pressure/vacuum, are there some rules of thumb when choosing one?

I should add at this point that there is a slight language barrier between the vendor and myself. My vocabulary doesn't run to anything technical.

R134a seems to be the preferred refrigerant in my part of the world.

Ta

[frank]

Visually, it is difficult to determine if a compressor works or not. I'm assuming that you are talking about small semi/hermetic compressors and not large machines?

Basic electrical tests - resistance and insulation tests, plus a smell of the oil and an oil acid test if necessary will give an indication to a pro whether or not to connect it into a system.

I would also be looking to see if the connections have been brazed up to prevent moisture ingress if it has come out of a working system.

[Wickfut]

Thank you for the advice. Would you recommend an oil change if the compressor has been laying around, unsealed, outside, probably in all weathers?

[frank]

In those circumstances, I wouldn't consider using a second hand compressor - it will probably have a short lifespan.

Given that you only want to 'experiment' then, with an oil change and a good vacuum, it should be OK for you.

[NH3LVR]

If it would be large enough for what you want to do you could purchase a functioning fridge and use the compressor from that.

[AlixNevis]

Good luck !

[DurdenJa]

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Keep ideas coming they are welcome!