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