this at the zoo?
We’ve got a Trane Chiller, Model #RTAA1854XT01A0C0F, I believe it’s 185 tons, air cooled condenser, with two separate circuits, circuit #1 is 100 tons, and circuit #2 is 85 tons. The problem we are having is circuit #1 will run for appx 30 sec. and cut out, the code we are getting is 194(Low Evap Rfgt Temp-Crtct 1). We are suspecting that the electronic expansion valve is not operating correctly because when circuit #2 starts the valve opens right before the compressor starts, however, circuit #1 does not; the compressor starts and the low side immediately pulls down to 10 inches of vacuum and cuts out. Head pressure remained constant at 150psi. Does anyone have any ideas as to what we should test, what kind of voltage should we read at the EXV? Would a bad sensor cause the EXV to not open? Hopefully Trane will come out and look at this Monday or Tuesday, but in the mean time, circuit #2 just can’t keep up with the load. Any help or ideas would be appreciated.
Still learning....
this at the zoo?
There are several things that can cause this problem. When you say it is pumping down to 10” of vacuum, are you going by your gauges, or the UCM? You can have a bad saturated suction temp or comp suction temp sensor. You can also have a bad EXV. You need to do an EXV test. This procedure, as well as many other tests, is in Trane Service Bulletin RTAA-SB-5 “Control Operation, Setup and Troubleshooting for RTAA Series R Air-Cooled Chiller Control Panel. UCM.”
I have this service bulletin in PDF format and I can Email it to you.
Yes, this is at the zoo, the 10" of vacuum was taken off the guages, not the UCM. txtraneman, if you could email me that service bulletin I would really appreciate it. agrossm@charter.net Thanks!
Still learning....
THANKS!! for the service bulletin, I'm going to look it over tonight, hopefully we'll have some answers tomorrow. I appreciate your help, Adam.
Still learning....
BTW, screws do not like being pulled into a vacuum, you might not want to keep doing it.
I am having a problem with a Trane chiller with screw compressors. We replaced the EXV and sensors for circuit 2, but as we were doing this circuit 1 went down on us. The first code said it was off on low superheat and then we reset it and it went off on low oil pressure. We checked the oil level and it looks good. The main thing we have noticed and its really aggrevating us is that none of the condenser fans will cycle on. The compressor will run for about 2 minutes until it reaches about 50psi suction and about 325psi head. We've checked all the fans and they check out good. Now we have narrowed the problem down to a bad circuit board. If anyone has had this problem and can give some advice I would really appreciate it. So would the 3000 soldiers who are living in the barracks, which are being supplied cooling from this chiller.
Have been the scourge of RTAA's. Also the umbilical to the EXV may have some broken wires due to vibration.
on fans staging....verify your outdoor air temp on the panel is reading within the actual days temp.it is located under the electrical panel repin it and take an OHM reading on it while out.do you have the manual on this machine
So you think that the outside air sensor may be loose or something? I'll make sure they are tight. We do have a manual, but I don't have it with me at the moment. Thanks for your reply. Also, thanks Rob10 I'll check it out.
check it at the pins and it wouldn't hurt to re-pin all the boots on all the modules with the disconnect down.do you have a Human Interface "tan" panel UCP-2 on the access door or the UCP-1 blue LED read out style inside the door?that oil pressure trip is the differential on the filter saftey switch that takes the difference on the oil into the filter and the oil going to the compressor...located up in the condenser above the compressor near the filter.
ok, I'll re-pin all the boots. That's the first thing I'll do in the morning. I'm not sure if I know what you mean by the UCP-1 or UCP-2. If you are talking about the display board, I think I have the UCP-2. I don't have much experience with this type chiller so apologize if it seems like i'm not on the same page. But the numbers and letters on the display are blue. Is that what you mean? The mechanics in the past had bypassed the normal oil line from the top by crimping the line and placing a refrigerant hose from the service valve by the filter to the pressure switch. I'm not sure why they decided to do that. Thanks
that's a UCP-1 you have and all the boards have the pins and all sensors you have on the 1st circuit are duplicated on the 2nd.the O/A is for the entire unit telling the main module how to stage and run with the ambient reading.
Yeah, thats the one I have. So, you think either the O/A sensor is bad or its not connected good? Thanks for your help.
if your reading the actual O/A on the panel then the sensor is connected and good!do the pin thing and restart the unit somebody else might kick in with some info by tommorrow.
I'll do that. I appreciate your help. This website is awesome.
Those condensor coils even when they look clean can be very dirty.These units when they start do a time/temperature deal so won't stage fans even if head pressure is 450#.Although one fan should start when compressor starts.Your suction pressure also is too low at S/U, the pins on those units are a PIA so pay close attention to the coonectors and make sure you can read the sensors when disconnected from the UCM.EXV tests can be done from the front panel so that is no problem checking them.The oil trip was because of the hi head pressure, when it gets that high it moves a higher volume of oil through the filter resulting in a larger than normal pressure drop.
Check your saturated condenser temp sensor. This could also cause your fans not to stage. Also, if the circuit is overcharged, you will subcool the refrigerant at the sensor and it will read low. The older RTAA's manufactured before mid 1995 didn't have an ambiant temp sensor unless an Eprom upgrade had been done. The UCM would look only at the temp differance between sat suct and sat cond temps and maintain a 70 PSI differential pressure. So, unit would always start with no fans and stage fans as needed. The newer chiller software will look at ambiant temp sensor before chiller starts and anticipate how many fans to run. After chiller starts and runs, it will look at pressure differential.
Thanks guys, I'll use all your suggestions. Is this a common problem with these? Its the first time I've had to work on this type chiller, so all your input is great. I'll let you know what I find tomorrow. Thanks
high trimbleOriginally Posted by ;571642
i need this service bulletin RTAA-SB-5
can u please e-mail it to me?
anw115@yahoo.com
thanks