I have a Trane RTAA0904XJ01A3C0BG that has circuit 1 continuously tripping due to "Oil System Fault-ckt 1". Now, there has been no recent repairs done to this circuit which could have brought in any contaminates, and the refrigerant charge is good. I'll be going in later to check oil level, but I know the oil filter on this system is generally oversized and shouldn't need replaced regularly (per the mfg), and there doesn't appear to be any leaks on this particular circuit (or even a history of leaks for that matter). Do any of you chiller pro's have any insight as to what a common cause is. I know this chiller verifies proper oil charge by means of the oil temp at the separator and the saturated condenser temp, and I believe it faults after 30 mins if there is lower than a 4 degree difference. What could cause this fault or restriction?