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R-22 freezer, Semi Hermetic Copeland
Got called out on a service call this Friday. It was a little mom and pop convenience/deli/grocery store by the wayside. They have an upright, 3-door freezer that was on the fritz, not cooling at all. I found the compressor head locked up, or I should say tight enough that I had to pulse the motor in order for it to turn over. It's a 1-1/2 hp semi hermetic Copeland. It's only 2 years old. R-22 POE oil.
The evap has electric defrost in the normal configuration. The evap is at top of the freezer chest and has a txv. The suction line is 5/8" and liquid line 1/4". There is no accumulator on the suction line, however, there is an evaporator pressure regulator, right before the king valve on the compressor.
I need to figure out what caused the compressor failure and correct it so the replacement comp doesn't follow suit. Obviously I couldn't take any p/t readings since the system is down. I have not yet tore the head off the failed compressor to see how the insides look. I know it has sufficient oil in the sump, as I could see it through the sight glass. About 1/3" from the bottom up.
I'm also unsure if this is an original r-22, or a converted r-12. I couldn't find the data plate on the freezer.
According to the research I did, r-22 is bad news for freezers. At 15°F the oil will separate from the refrigerant and just kind of float on top and doesn't want to return from the evap correctly until it is forced out in globs. I'm thinking a properly sized accumulator may be in order. Also r-22 has a high heat of compression ratio, and in a freezer application that has a low suction pressure, the discharge temp can go out of bounds. That would require a liquid injection valve to cool the suction gas temp.
If I do put in an accumulator, would it be advisable to put a small heat band around the bottom of it to prevent defrost flooding and help the oil move? Should I consider installing a liquid injection valve? Should the EPR be removed if I do this stuff?
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