acnerd
29-07-2009, 06:05 PM
I spend most of my life on Japanese split systems, but today I had a look at a Ciat chiller on a regular maintenance visit. It's a 70kW chiller with air cooled condenser and 2 recip compressors on one fridge circuit. No faults indicated. R22. Recips are 3 cylinder with one cylinder on each compressor having an unloader. I noticed bubbles in the sight glass, so took the following readings:
One compressor running:
Suction pressure 64 psi
Suction temp. 12 C
Liquid pressure 195 psi (on liquid line)
Liquid temp 35 C
Air on condenser 22 C
Air off condenser 33C
CHW flow temp 8 to 11C
CHW return 12 C
Both compressors running:
Suction pressure 60 psi
Suction temp. 7 C
Liquid pressure 255 psi
Liquid temp 46 C
Air on condenser 22 C
Air off condenser 40C
CHW flow temp 6 to 9C
CHW return 11 C
Because of very small demand on the system, thanks to rubbish UK summer, the chiller will only run for about 5 minutes before reaching setpoint.
Question: is it short of refrigerant (subcooling quite low) or am I not giving it enough time to "stabilize" or am I missing the plot completely?
PS: we have to assume flow rates through evaporator are ok. Condensor coils are clean, half of the 8 fans run, even when 2 compressors running. Let me know if you need more info. Thanks.
One compressor running:
Suction pressure 64 psi
Suction temp. 12 C
Liquid pressure 195 psi (on liquid line)
Liquid temp 35 C
Air on condenser 22 C
Air off condenser 33C
CHW flow temp 8 to 11C
CHW return 12 C
Both compressors running:
Suction pressure 60 psi
Suction temp. 7 C
Liquid pressure 255 psi
Liquid temp 46 C
Air on condenser 22 C
Air off condenser 40C
CHW flow temp 6 to 9C
CHW return 11 C
Because of very small demand on the system, thanks to rubbish UK summer, the chiller will only run for about 5 minutes before reaching setpoint.
Question: is it short of refrigerant (subcooling quite low) or am I not giving it enough time to "stabilize" or am I missing the plot completely?
PS: we have to assume flow rates through evaporator are ok. Condensor coils are clean, half of the 8 fans run, even when 2 compressors running. Let me know if you need more info. Thanks.