Oil System Fault (Trane RTAA Chiller)

[randystoker]

I have a Trane chiller model # RTAA0704XN01S300BN, Serial # V02J06868. Both circuits have repetitive failures from "oil system fault". Both oil temperature sensors have been replaced and the condensers have been thoroughly cleaned. After cleaning, seen reduced failures with circuit A, but no change with circuit B. Also, noticed that circuit A has entering oil temperature of 110.4F and circuit B has entering oil temperature of 75F. Past problems: Circuit "A" was showing below freezing temperature on oil, but problem was remedied after oil temperature sensor was replaced. Any input on what could be causing this?

[jayguy]

I have a Trane chiller model # RTAA0704XN01S300BN, Serial # V02J06868. Both circuits have repetitive failures from "oil system fault". Both oil temperature sensors have been replaced and the condensers have been thoroughly cleaned. After cleaning, seen reduced failures with circuit A, but no change with circuit B. Also, noticed that circuit A has entering oil temperature of 110.4F and circuit B has entering oil temperature of 75F. Past problems: Circuit "A" was showing below freezing temperature on oil, but problem was remedied after oil temperature sensor was replaced. Any input on what could be causing this?

assuming the oil temperature sensors are correct...you need to look at the saturated evap temp and compressor temp sensors. if they are wrong, then you could flood back (the compressor won't care), however, you will be putting liquid refrigerant into the oil separator. as the liquid boils off, it pre-cools the oil before going into the oil cooler portion of the condensor. this makes the oil temp colder than the saturated condensing temperature...which is the reason for the diagnostic.

[randystoker]

Your diagnosis was exactly on the mark! The "oil system fault" failure is not a problem anymore. Thanks for the help!!