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13 degree Delta T

I have a Rheem 3 ton air handler and a 2 1/2 ton condensing unit - a 14 degree Delta T. Ambient temperature 85 degrees, suction pressure 70, head 210, txb valve, discharge temp high side, 158 degrees, exiting cu coil 101 degrees, entering txb 96 degrees, vapor line exiting evaporator coil 67.5 degrees. Before service port 71.2 degrees, indoor wet bulb temp is 68, copper size 3/8''/3/4'', overall copper run is 25'.
Why is there a 13 degree Delta T?

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I assume r-22 refrigerant by the pressure... you have a saturate temperature of approximately 41 degree and 71 degrees at the service port this equates to a 30 degree superheat. a condenser saturation temperature of 105 degrees and since the liquid line temp at the service valve is not given only the enterin indoor coil on the liquid line a 96 degree temperature this would equate to a subcooling temperatureof about nine degrees. You have too high of a superheat reading. verify that the bulb for the txv is correctly positioned and insulated. if it is then you need to remove the bulb from the suction line, hold it in your hand to warm it up and see if the superheat changes. you could also have issues with your ductwork. If the supply temperture is around 50-55 degrees then the unit is doing all it can.. Check the txv and the ductwork as the subcooling indicates that the condenser side is doing it's job, but the superheat readings indicate that you are starving the evaporator..

Posted on Jul 28, 2009

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What is the humidity in your home?
105 condenser saturation temp - 85 outdoor ambient is a 20-F temp-rise which indicates a high humidity heatload in your home.

that will lower the indoor temp-split.

Could be working close to normal except if it has a TXV the superheat should be much lower at the mfg'ers number 7 to 12F. - udarrell

Posted on Jun 12, 2012

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