Trane Series R Chillers

[zigmund]

Am about to begin investigating chronic low evaporator pressure trips in 3 Trane Series R's (parallel) used for Calmac Ice Storage system. All 3 trip intermittently. Any ideas anyone. Possible suspects: TEV's , flow rate through evap , poor heat transfer ie. fouled evap , excessive glycol concentration , laminar flow through evap . Anything else I'm missing? Appreciate any info. Thanks.

[mustardman]

Evap flow and low condenser entering water temp are where I would start. If all three machines are doing it it definitely seems like a system problem to me I would doubt strongly that all three chillers have the same problem. Do the trips typically happen at start up or during bormal running conditions. More info please.

Good luck

[zigmund]

I start tomorrow, but one thing I do know is that they let the condenser water temp drift down with the ambient outside temp plus cooling tower at night when in ice making mode. This results in cond temps probably in the low 60's. They maintain 80 when in regular chilled water mode during the day. I was told that at night with the low evap temp the low cond temp still mainained enough of differential. I wonder.

[zigmund]

Oh, by the way this job is in Honolulu. The trips happen well into the operating period usually.

[mustardman]

I know from numerous experiences that those machines do not like cold condenser water at all. How often do these trips occur. If it is daily during these low ambient conditions well low for hawaii anyways I would have the customer reset the ddc to maintain a 70-75 degree entering condenser water temp. It will either confirm or eliminate this possibility. And allow you to focus on a chilled problem. Typically low condenser water shows up as an oil problem at start up but if you are running cold could be you are stacking refrigerant in the condenser. Try it cant hurt anything.

[jayguy]

Oh, by the way this job is in Honolulu. The trips happen well into the operating period usually.

Honolulu? well, boo-hoo! it got to a high of 8F today...warm front :D seriously, though, good for you...i would love for it to be warm enough for me to be working on a running chiller...now i got FBS (frozen butt syndrome).

like MM said, probably a system problem. i would also check the programming. i found a couple of RTHB's that were programmed for water trip points but had glycol in them. after resetting them, no more problems.

having the tripping happen well into the operating period would indicate: evap fouling and water flows (including intermittant, during a shutdown, etc.)

good luck.

[zigmund]

Will do. Will post more info after tomorrow. Thanks for the help!

[stickerhead]

I have been fighting the same problem with two RTHB's. You said R series but not the type. The "B's" that I have do it because the EXV algorithum is controlled by the discharge gas superheat. In ice mode, the discharge gas will drop cousing the EXV to close knocking it off on low pressure with the low temp set at 14 degrees. It runs great in conventional mode. I have been playing around with the refrigerant charge to raise the DG superheat to allow the valve to open more but not effect the daily run mode. I have also checked for exceesive oil in the system to make sure it is not oil carryover with refrigerant. I have played with the PID loop and it only prolongs the problem. One off the things I have not done is checked for evap tube fouling. It sounds strange but if the glycol is not checked for inhibitors, it can foul. Your condenser water is too cold at nite for ice storage. Try to maintain the same temp you do during the day. I have trimmed some gas out below name plate charge and it has worked. I pulled it from the liquid line a little at a time while it was in ice mode and watched the EXV. The I re-checked it during conventional mode. Approach was ok. I can tell you the factory does not have a clue. Had many a conversation with them. I hate RTHB's, rather have a RTHA.

[maxster]

are you all 3 running and if not are you isolating the off machine on the evap and cond during during the cycles.

[jayguy]

I have been fighting the same problem with two RTHB's. You said R series but not the type. The "B's" that I have do it because the EXV algorithum is controlled by the discharge gas superheat. In ice mode, the discharge gas will drop cousing the EXV to close knocking it off on low pressure with the low temp set at 14 degrees. It runs great in conventional mode. I have been playing around with the refrigerant charge to raise the DG superheat to allow the valve to open more but not effect the daily run mode. I have also checked for exceesive oil in the system to make sure it is not oil carryover with refrigerant. I have played with the PID loop and it only prolongs the problem. One off the things I have not done is checked for evap tube fouling. It sounds strange but if the glycol is not checked for inhibitors, it can foul. Your condenser water is too cold at nite for ice storage. Try to maintain the same temp you do during the day. I have trimmed some gas out below name plate charge and it has worked. I pulled it from the liquid line a little at a time while it was in ice mode and watched the EXV. The I re-checked it during conventional mode. Approach was ok. I can tell you the factory does not have a clue. Had many a conversation with them. I hate RTHB's, rather have a RTHA.

are these chillers from pre-1996?

[zigmund]

These are RTHD's. Now Running condenser at 75 deg. Let me take a look at these other items in your post and I'll get back to you.

[zigmund]

All 3 units run in ice mode. For conventional mode the units are equipped with both evaporator and condenser isolation valves.

[zigmund]

These units are brand new installed in August , put into operation in Sept.

[r404a]

I have been fighting the same problem with two RTHB's. You said R series but not the type. The "B's" that I have do it because the EXV algorithum is controlled by the discharge gas superheat. In ice mode, the discharge gas will drop cousing the EXV to close knocking it off on low pressure with the low temp set at 14 degrees. It runs great in conventional mode. I have been playing around with the refrigerant charge to raise the DG superheat to allow the valve to open more but not effect the daily run mode. I have also checked for exceesive oil in the system to make sure it is not oil carryover with refrigerant. I have played with the PID loop and it only prolongs the problem. One off the things I have not done is checked for evap tube fouling. It sounds strange but if the glycol is not checked for inhibitors, it can foul. Your condenser water is too cold at nite for ice storage. Try to maintain the same temp you do during the day. I have trimmed some gas out below name plate charge and it has worked. I pulled it from the liquid line a little at a time while it was in ice mode and watched the EXV. The I re-checked it during conventional mode. Approach was ok. I can tell you the factory does not have a clue. Had many a conversation with them. I hate RTHB's, rather have a RTHA.




Stickerhead,
I am no RTHB expert by anymeans. I know that the EXV does control to discharge superheat, but it is not the only mitigating factor. If memory serves me right, split on the evaporator plays into it as well.


r404a

[james2007]

Does it shutdown at the starting. the picture maybe helpful.
http://rapidshare.com/files/80501532/RTHD.JPG.html

[stickerhead]

404, you are correct, it looks also at evap. delta T.

[zigmund]

Some additional info. 26% glycol, evap pressure 20 psi, evap approach 2.8 deg, evap flow 1100 gpm.

[zigmund]

which trip points specifically?

[zigmund]

usually, but sometimes later.

[Healey Nut]

Probably low load once the ice banks are reaching capacity and cold tower water . RTHD's do not like cold tower water .

[OzziePedro]

With them being RTHDs you should be able to get logs from the CH530. This can allow you to see a whole load of info at the same time. It looks like it's common to all 3 chillers so my guess would be as previously stated flows and condenser water temps. You could even go to with fitting an actuator to the cond valves and using the output from the CH530 to maintain a good cond pressure.

[jayguy]

With them being RTHDs you should be able to get logs from the CH530.

i was thinking the same thing...you could also email that log to Pueblo or myself if you really got stuck.

you only mentioned a few technical data points...we will need much more to help troubleshoot this issue...unless you got it figured out.

good luck.

[zigmund]

Flows are solid at 1100 to 1200 gpm, condenser water constant at 78 deg. I'm working with Trane Pueblo presently. Thay are aware of the problem and have been working on a revised control program to remedy the situation. It has to do with the overly aggressive compressor loading by the slide valve and its subsequent failure to respond in a timely and accurate manner.

[acjourneyman]

I don't have a manual handy but I thought that the RTHB in ice mode,like extended unloading, did not look at the discharge superheat.I believe they just drove the slide valve open 100%.It has been a long time since I have seen an ice making chiller so I am probably wrong.I guess the other thing is controls, how many chillers running, what kind of load, and like others have mentioned, tower temps.

[zigmund]

You are right and that in essence is the source of the problem. The slide will not respond when it needs to.To current limit, evap conditions, etc. At least thats what the guys at Pueblo are telling me. They say they have been working on this for several months. With instances occuring at various locations. They have been testing a fix on some machines in Brazil and China.

[acjourneyman]

I think than in ice making mode you need to enable an ice making input into the board and it goes balls to the walls, when you have reached setpoint you need to disable the input and it will return to reg mode or will shut down.