View Full Version : RTHB150 low refrig temp prob
10-12-2011, 08:25 AM
Have a Trane chiller RTHB150. If the EXV mini travel is set at 18%, will the actual EXV % open still drop below this set point? EXV is shutting right down to some 1% causing low refrig temp faults. I believe EXV maxi travel setpt is 1670 steps for this model! Have recently pulled the gas, repaired leak and weighed gas back in, as per name plate. Any input would be great. Thanks.
10-12-2011, 11:48 AM
been a while since I have worked on any RTHB's, I have all ''D'' machines, but have you checked your sensors for proper readings, could be getting wrong temp and trying to raise S/H. And you have verified H2o flow.
10-12-2011, 07:43 PM
dont forget that trane changed some of the refrigerant and oil charges...see attached.
i don't remember there being a 'minimum travel stop'. there should be a 'maximum travel setpoint', 'exv closed stop' and 'exv open stop'...what are those values?
10-12-2011, 08:04 PM
"The EXV Minimum Travel Stop is only active in the Extended Unloading mode, with your EXV Maximum Travel Setpoint set to 1670 the EXV will never physically close 100% through commands of the UCP2"
Attached explains it better and in fewer words than I could, however if you post a full load log of the chiller I can review and comment.
10-12-2011, 08:22 PM
Check that all sensors are reading correctly. Does it ever run in evap. limit? If so check the evap. water flow, if O.K. check the evap. tubes to see if they are fouled.
10-13-2011, 12:24 AM
Trim charge dude. It's that simple. Ignore the nameplate and trim to get the EXV to stay open.
10-27-2011, 06:47 AM
Just to let you all know how I went with the RTHB150 / U97C09777. Checked over all sensors, resistance and voltage. Even used the ice water method, all o.k. Checked full EXV operations, measuring voltages when driving etc, all o.k. Water flows all o.k too. Manually adjusted the EXV to 60% open, allowed chiller to run, found discharge superheat sitting around 5 degrees C and not rising up to s/h control point of 20.5 degrees C.
Removed 10kgs of refrigerant, ran again in EXV auto mode, still found EXV shutting down to 5-6% and after an hour or so tripped out again on low evap refrig temp. Removed another 5kgs and tested again. Min EXV shut down was 9.3%, but mostly around 12-14%. Lowest Evap refrig temp dropped to 0.7 degrees C, but then increased. Discharge S/H sat around 20-22 degrees C. Left at that, been more than a week now with no problem.
I did check out the bulletin, and it stated the revised charge for this model was from 300 lbs to 285 lbs, which is labelled on name plate. So possibly still not correct! Thanks for all the input. Cheers.
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