Got a warranty call from a national food processor. Their 2 door upright refrigerator located in the quality control laboratory not cooling. Unit was diagnosed with a plugged cap tube. The factory sent out a new compressor,cap tube, and drier. The tech installed everything and Weighed in the R290 refrigerant. Now 2 Months later the factory discovers that they sent out the wrong compressor. Now here’s my question. How could this work correctly for two months. This is in a lab and they record temperatures every hour. They have record sheet taped to the door. And are using external medical thermometers.Talked to the Tech and he says the process tubes suction, hot gas were exactly the same as the original compressor. So he didn’t think anything was wrong. The factory is sending out correct parts for us to redo.
Ooopps, Installed 134A compressor on a R290 system
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tarzanseal
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Let's recap the situation.
OP has a medium temperature cooler which was manufactured with a R290 compressor and appropriate gas.
Compressor gets replaced with a R134a compressor and R290 gas.
In lieu of removing the compressor I would consider replacing the R290 gas with R134a and trim the cap tube.
For example lets imagine a 1/3 hp at 20°f SST.
As you can see in the chart below you could trim 2' off of the cap tube and be pretty close.
I couldn't find a readily available R290 cap tube chart but will use R22 and R12 which is very close to R134a.
OP has a medium temperature cooler which was manufactured with a R290 compressor and appropriate gas.
Compressor gets replaced with a R134a compressor and R290 gas.
In lieu of removing the compressor I would consider replacing the R290 gas with R134a and trim the cap tube.
For example lets imagine a 1/3 hp at 20°f SST.
As you can see in the chart below you could trim 2' off of the cap tube and be pretty close.
I couldn't find a readily available R290 cap tube chart but will use R22 and R12 which is very close to R134a.
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I have searched and searched for any tech sheets for sizing cap tubes for R290. I can only say from what I have seen. The manufacturers are using smaller compressors, with smaller piping, and far less power draw on these 290 units, to achieve, in many cases better performance. R290 out performs ANY of the HFC, or HCFC refrigerants out there. I am betting that C3H8 flows better through the piping, the compressor doesn't have to work as hard, and I am betting the cap tube ID is smaller. If retrofitting an HCFC to an HFC, you can get away by just adjusting your charge, trying the same method to or from propane, not something I would try.
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Uh huh .... you could definitely mess around with the cap tube length .. but .... what if you did that ... only to find out the Condenser Coil is too small to reject the heat of 134 ?
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I agree, those r290 condenser coils are way small, usually one pass of loops. but it wont take much to trim off and see what happens but not as easy to add back to if the head is too high and not condensing the way it should.
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Can you post the link where this came from?
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Tecumseh? I know I recognize that paragraph.They make engines too
Why would there be any more heat rejected with 134a than R290?
Any time I've changed compressors/switched refrigerants the balance points were nearly identical to the expected result.
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I agree. I've heard although it never made a lot of sense to me that if you go to a higher pressure refrigerant you'll need more condenser but in this case you'd be going to a lower pressure refrigerant I believe so I don't see the problem.
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It wouldn't matter, higher or lower pressure refrigerant. The heat being rejected is equivalent to the heat being absorbed by the evaporator plus the heat of compression from the compressor.THIS
R134a being a lower pressure refrigerant compared to R290
There may be a slight difference in performance due to the mass flow requirements of the new refrigerant, but overall it'll operate at about the same saturation temperatures if the capacity of the compressor for the new refrigerant is the same as the capacity of the previous compressor with the old refrigerant.
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1995 when the lovely Government outlawed R12 in Vehicles .... I was a Mechanic ... and found some vehicles would swap over to the 134a with no problem , and others you would have the head pressure way to high
Soon after that ... a company began offering aftermarket condensers that solved this problem ... they looked like a Micro Channel made of aluminum
Will a R290 swap to 134 work ? I have no idea ... but ... I happen to have a 2 door cooler sitting in the garage that I can test with :yes:
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it might be less pressure at the same amount of refrigerant but how much more refrigerant must you add to make it work in that system, maybe 5X just to get the subcooling where you want because of the smaller condensor? The additional refrigerant would make it more pressure on the cap tube meaning you would be flooding back big time, cut that captube like you talking about and your pressures may be right,but eventually you are talking bad compressor from floodback.
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Do it , do it , DO IT!That deserves a new thread!
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