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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 948
Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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I have a 4 ton r-410 A/C compressor I think I'd not pumping

Customer Question

I have a 4 ton r-410 A/C compressor I think I'd not pumping properly.How do I test it?
Submitted: 2 years ago.
Category: HVAC
Expert:  Brian HVAC Guy replied 2 years ago.

Hi I'm Brian and I'm here to help!

The easiest way to check if the compressor is pumping ok is to front seat (close) the liquid line king valve and see if the compressor will pump all the refrigerant into the condenser and then even into a slight vacuum on the suction side. Most systems today are scroll type compressors and they either pump or they don't, there's really no in between like years ago with the reciprocating compressor with reed valves. There are no valves to go bad on a scroll compressor. I would think your issue is somewhere else. Duct leakage is a commonly overlooked problem. Taking the temperature of the suction and liquid lines at the outdoor unit and the high and low pressures when you take the temperature readings will be very helpful for me to help you diagnose what may be going on.

Please reply if you have further questions about this. Otherwise, please remember to rate positively (3 stars or better) before you leave! Bonuses are welcome and very appreciated!

Thank you,
Brian

Customer: replied 2 years ago.
As I said the return air temp at the Air Handler is 78 degrees and the supply air is 62 .I have 16' superheat and 13' sub cooling at the condensing unit. I need a Copeland Engineer to tell me if this compressor is inefficient or not.thank you.
Expert:  Brian HVAC Guy replied 2 years ago.

I am not a Copeland Engineer, I am a highly skilled and trained industrial/commercial/residential HVAC technician. I don't believe we have a Copeland Engineer online at the moment. To determine actual efficiency of the compressor you would have to provide a great deal more info. A factory Copeland Engineer (or anybody else for that matter) would not be able to provide compressor efficiency without measured airflow in cfm, actual compressor current draw, actual voltage readings, indoor, outdoor and supply air wet and dry bulb temperatures, hot gas line temperature and liquid and suction temperatures/pressures. You've provided some of these but not all. Your question is more about system efficiency

I saw the supply air and room temperature readings. I didn't ask for those again. I asked for the temperatures of the liquid and suction lines to determine superheat and subcool. Thanks for providing the superheat and subcool. If those are accurate, I would say your compressor itself is at proper efficiency and is doing it's job. A compressor amp draw and the compressor FLA would help confirm that. Your system as a whole, however, is not producing the desired results. Your subcool is fine but your superheat is a bit high, your suction is also a bit high as well as your supply air temperature. All of these put together don't point to a compressor issue. It sounds like your evaporator is starving for refrigerant or it is overloaded with heat load or both. I know you said you replaced the txv but if the txv is adjustable, ensure the txv bulb is secured properly to the suction line. With the subcool you have, I would think you should have a solid flow of liquid refrigerant to your txv so I would try adjusting your txv in for a lower superheat to flow more refrigerant and lower the superheat. This may initially raise the suction pressure but the suction will drop when the temperatures come more in line. Are you sure the air handler is 1/2 ton larger than the condensing unit? The readings you gave make it look like the reverse. Evaps are rarely undersized from the condenser. It is not an accepted practice. If you are moving too much evaporator airflow you will get the operating conditions you're experiencing. You may need to lower evap airflow. I would also look carefully at the return duct for leakage. This would overload the evap and give the same results you're seeing. It's also possible you could be slightly low on refrigerant but the subcool would indicate otherwise so I would check everything else first.

Let me know how I can help further.

Thanks,

Brian

Expert:  Brian HVAC Guy replied 2 years ago.

I am not a Copeland Engineer, I am a highly skilled and trained industrial/commercial/residential HVAC technician. I don't believe we have a Copeland Engineer online at the moment. To determine actual efficiency of the compressor you would have to provide a great deal more info. A factory Copeland Engineer (or anybody else for that matter) would not be able to provide compressor efficiency without measured airflow in cfm, actual compressor current draw, actual voltage readings, indoor, outdoor and supply air wet and dry bulb temperatures, hot gas line temperature and liquid and suction temperatures/pressures. You've provided some of these but not all. Your question is more about system efficiency

I saw the supply air and room temperature readings. I didn't ask for those again. I asked for the temperatures of the liquid and suction lines to determine superheat and subcool. Thanks for providing the superheat and subcool. If those are accurate, I would say your compressor itself is at proper efficiency and is doing it's job. A compressor amp draw and the compressor FLA would help confirm that. Your system as a whole, however, is not producing the desired results. Your subcool is fine but your superheat is a bit high, your suction is also a bit high as well as your supply air temperature. All of these put together don't point to a compressor issue. It sounds like your evaporator is starving for refrigerant or it is overloaded with heat load or both. I know you said you replaced the txv but if the txv is adjustable, ensure the txv bulb is secured properly to the suction line. With the subcool you have, I would think you should have a solid flow of liquid refrigerant to your txv so I would try adjusting your txv in by turning the adjustment screw out for a lower superheat to flow more refrigerant and lower the superheat. This may initially raise the suction pressure but the suction will drop when the temperatures come more in line. Are you sure the air handler is 1/2 ton smaller than the condensing unit? The readings you gave make it look like the reverse. Evaps are rarely undersized from the condenser. It is not an accepted practice. If you are moving too much evaporator airflow you will get the operating conditions you're experiencing. You may need to lower evap airflow. I would also look carefully at the return duct for leakage. This would overload the evap and give the same results you're seeing. It's also possible you could be slightly low on refrigerant but the subcool would indicate otherwise so I would check everything else first.

Let me know how I can help further.

Thanks,

Brian