Since it is a heatpump there is a possibility that the outside coil's check valve has stuck in a "partially open position." It would also could force some refrigerant through the outdoor expansion valve to the condenser coil. In the cooling mode this will result in low suction pressure and low discharge pressure. Sub cooling would be extra high.
Originally posted by book
Today I was doing a maintenance check on a three year old Carrier "Heat Pump" M# 38YKCo36 321 S# 4202EO2360. The high sub-cooling puzzled me. You see the unit lable listed an indoor sub-cooling requirement of 15 degrees. I started with a sub-cooling of 27 degrees. So removed 1 lb. of R-22 and resulted in following conditions: OAT-78, WB-58, LLP-240psi, LLT-89, SLP-60, SLT-46, Return Air- 70, Supply Air- 47 delta-T 23. The compressor amp draw was 17A and system has a TXV on coil. I tried to remove more freon to reduce SC more but suction pressure would drop below 60 and Sub Cooling remained right at 25 degrees. Any suggestions why SC remains high while suction pressure drops so low? I have experienced similar situations to this before on some units, when trying to charge a TXV by sub-cooling to the unit label listing.
The condenser was washed clean and indoor air handler and coil is three years old with clean filter and no outward sign of dirty coil. That is, blower and return air compartment are clean.
[Edited by book on 07-19-2005 at 11:04 PM]