Posted this one a while ago. Went through all the checks of refrig, oil and eprom upgrades as per bulletins. Trane: RTHB150ULFOONWR / Ser: U97CO9777. Obviously a 1997 model, so no adjustments are required on the refrig and oil charge.
Found refrig leak on liq line refrig filter element connection. Removed all refrig, found 65kgs short, total should be 285lbs (130kgs). Replaced oil filter and the refrig filter element (Part No: FLR 03018) Original filter I removed was P/No: FLR 0860. According to Trane spare parts (Dalkia) here in Melbourne the 03018 is the replacement for the 0860. Would anyone know if this is correct? It took them three attempts to finally send me the correct one (I hope).
Once correct amount of refrigerant was weighed in, started chiller. Have had constant faults of low refrigerant temp. Some days it can run for a few hrs, before failing. Have removed and checked all sensors, voltage and resistances, all o.k. Discharge superheat will read extremely low, so EXV closes down, even to 0% sometimes. Have even tried removing 5kgs, tested, then other 5kg of refrigerant. Did run alot better for a while, with disch superheat maintaining control set point and Exv sitting around the 15-20% open. After a few days, started failing again on low refrig temp. See details:
Evap press:412kpa, disch:1256 kpa, Sat evap refrig temp:0.7 degrees C, sat cond temp: 34.9 , comp discharge temp: 52.7 , disch s/heat: 16.9 , disch s/heat control set point: 22.6 , EXV open %: 9.3 , steps open: 156 , evap approach: 5.7 , cond approach: 1.2 , evap ch water ent: 10 degrees C , evap ch w leave: 6.6 , cond water ent: 27.1 , cond water leave: 33.2.
The condenser water uses only a throttling valve, no by-pass at c.tower, which is controlled by a separate siemens controller that someone has fitted in the past. This controller reads the system discharge pressure which drives the throttling valve.
Would it be better for the chiller to operate this throttling valve? Would this set up be causing problems trying to maintain the discharge superheat setting? Maybe the chiller thinks it is still driving the throttling valve, but making no effect in raising the condenser water / discharge superheat temp, therefore using the EXV instead?
Would anyone have any other ideas about this headache I have? Would be greatly appreciated. Cheers.