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Discussion Starter · #1 ·
Hello All,

Im a lab technician and test HVAC systems in a psychrometric lab and have had a reacurring problem in my cooling equipment in my outdoor (OD)room. When running a LAC(Low Ambient Control) test with my OD room at 25°F, my OD cooling equipment shuts off on internal overload with Compressor dome temperatures getting up to 300°F before they shut off. I know this is not the best on the compressor would like to get it lower so that they are able to run more efficient and cool my OD room better with out shutting off. They system Im using is a 5-ton R22 system. My condensing coil is a water coil instead of a air coil and my evaporator is a air coil. My compressor also receives no airflow over it so this does not help with it overheating. Any tips or suggestions you may have in getting my Compressors to run without overheating would be much appreciated.

Michael
 

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The compressor is a vapor cooled compressor, so it doesn't need any air flow over it.

If your using a standard water cooled A/C condenser to cool your OD room to 25°F. Its not getting enough cold refrigerant vapor back to it, to keep it cool.

Does the system have a hot gas bypass to keep the indoor coil from freezing? If so, it may be bypassing too much hot gas. So you may need to add a liquid injector to the vapor line to cool the compressor.
 

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Discussion Starter · #3 ·
Thank you for your response.
It is not a hot gas bypass compressor and I feel like I should be able to get them to work without installing one.
I also do not have problems with my evap coil freezing. I just have problems with high SH and them going off on internal overload.

Michael
 

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Thank you for your response.
It is not a hot gas bypass compressor and I feel like I should be able to get them to work without installing one.
I also do not have problems with my evap coil freezing. I just have problems with high SH and them going off on internal overload.

Michael
Using a high temp/comfort cooling metering device, you will have high SH. If you get the Sh down, you will have freeze up problems. A/Cs are not made to lower a room temp to 25°F. So you either have to modify it, or change out compressors on a regular basis as they burn out.
 

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So by modifying I was looking as changing my cooling TXVs. What would u suggest for modifying it?
Adjustable medium temp TXVs. Along with increased CFM across the cooling coil. To reduce frosting.
 

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Discussion Starter · #7 ·
What about changing the system to a different refridgerant. Is there one that could perform better for me?
Another variable to consider is the pin valve on the water coil. What is its roll in this if any?
 

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You would still have a high SH with a different refrigerant. By pin valve, are you referring to a pressure regulating valve.
 
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