Dear All,

I have the weirdest situation in my test bench for a 4x scroll compressor (Bitzer GSD80385) 2 circuit air cooled water chiller.

The design dT water in out is 5C. both circuits are equipped with identical elements, all piping guides are the same- same diameter etc nothing is different.

Both circuits are charged with 18kG of r410a. One of the circuit is giving excelent cooling capacity 2,5C. The other circuit is giving 0,7C of cooling. The superheat values are normal, EXV is modulating. I write the conditions of both circuits below:

circuit 1:
Water inlet:10C
Water Outlet: 7,5C
Evaporating Pressure: 7,1Barg
Discharge Pressure:23Barg
Superheat:7K
EXV opening state:%58
Subcooling:1K


circuit 2
Water inlet:10C
Water Outlet: 9,3C
Evaporating Pressure: 7,7Barg
Discharge Pressure:24Barg
Superheat:7K
EXV opening state:%95
Subcooling:1K

I have made also comparison for discharge - liquid line equipments pressure drop values;

Circuit 1
microchannel condenser inlet-outlet pressure drop: 1,0Bar
Dryer cartridge inlet-outlet pressure drop: 0,07Bar

Circuit 2
microchannel condenser inlet-outlet pressure drop: 1,5Bar
Dryer cartridge inlet-outlet pressure drop: 0,20Bar

First i replaced the compressors with the new ones as it was the only thing that made sense to me; nothing changed after replacement. After finding that i have excessive pressure drops on discharge line i thought about restricted condenser and dryer so i replaced both the condenser and the dryer cartridge with new ones.

Unfortunately the result is the same. 0,2Bar , 1,5 bar pressure drops, 0,7C cooling(almost 1/4 of required capacity).

I appreciate any advise and thoughts- really feel helpless