I have a Trane CGAM chiller (CGAM070F), serial # U09M13536, Refrigerant R-410A, that has one circuit (two parallel compressors) with the capacity limited by compressor discharge temp. I observed that when the 2nd compressor in the affected circuit came on, the high-side pressure built up to 417.4 psig and discharge temp rose to 120F and then the circuit drops to only one compressor and the display board (Tracer CH530) again indicates capacity is again limited by high discharge temperature. Checking the manual, is simply indicates the discharge temperature should be 63F or more and the condensing pressure should be 420 to 440 psig. However, it never gets to that condensing pressure range when the capacity again is limited.

The other circuit of the chiller indicates it is off on high pressure and will not reset. This chiller service call came after the 2nd hit and severe rain downpour from the remnants of Isaac.

I have the same model/size chiller at another location and experiences the same capacity limit by high discharge temperature on one circuit and had the condenser cleaned with no change. Both chillers have all condenser fans operations and showing 100% air flow.

What could be the problem?