We have Trane RTHD in our plant which is installed 2 months ago.We are having oil loss at compressor problem.We are using directly river water in condenser and we have a variable cooling need conditions.The river water temperature is 11-13 C in this winter.Altough head pressure,oil pressure,refrigerant luquid level is OK we sometimes face oil loss problem.

Evap entering water 1.2C
Evap leaving temp -2.8C
Condenser entering water 12C
Condenser leaving water 13C

Evap refrigerant pressure 136
Condenser ref. pressure 400

Evap app. temp : 3-4 C
Condenser app. temp: 1-2C
Load: %42

Chiller works in above conditions about 75-80 minutes.Then as we dont have cooling need so much it goes to;
Evap entering water -1.7C
Evap leaving temp -3C
Condenser entering water 12C
Condenser leaving water 12.5C

Evap refrigerant pressure 128
Condenser ref. pressure 360

Evap app. temp : 2 C
Condenser app. temp: 0.8C
Load: %26

But after working 6-7 hours while in above conditions the chiller goes to "oil loss"
İs this because of cold condenser water?If I can warm it up to 20 C then is everthing going to be OK?

Many thanks for asnwers