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  1. #14
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    Jan 2011
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    Central, PA
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    Quote Originally Posted by valdelocc View Post
    The resistance checked OK, I also, locked compressor 2, switched the EXV control wiring from EXV-2 to EXV-1 and circuit 1 ran fine using the inputs and outputs of loop 2, that pretty much eliminates sensor issues.
    I am sure I am missing something here, but how did you run the circuit one compressor using inputs from circuit 2 which is not running? Compare the actual readings with the readings in the display.

  2. #15
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    Oct 2007
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    Southern Indiana
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    Quote Originally Posted by valdelocc View Post
    You may have a valid point, I think you are talking a bout the lip seals leaking, right? I cant see how a leaky lip seal can cause the loop to trip on "low refrigerant temperature" alarm.
    I know you are trying to help and Im thankful for that.
    Yep that's what I'm talking about, there's some other seals also if I remember correct that can cause similar problems. I realize it's hard to believe but I had two chillers last year going off on low refrigerant temp, I went through everything on them until I called tech support and they forwarded my call to publeo, Co where the chillers are made. They talked me through it and sent me all the service bulletins to diagnose it. We even had a factory Trane tech come down and verify it.
    I'm not saying that the chiller your working on couldn't be something else, just sayin it's worth looking into. I would suggest giving tech support a call and tell them what's going on and see if they can send you the service bulletins.

    It makes pretty good sense really if you think about it. If the compressor is loaded and trying to pump a lot of gas and the exv is barely open its going to drop the suction pressure real low real fast which is why you get the low refrigerant temp alarm.

  3. #16
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    Central, PA
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    How would an expansion valve that is barely open throw a low refrigerant temp fault in 20 seconds?

  4. #17
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    Nov 2004
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    up in the hizzy
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    Quote Originally Posted by jabeu View Post
    I am sure I am missing something here, but how did you run the circuit one compressor using inputs from circuit 2 which is not running? Compare the actual readings with the readings in the display.
    I ran both compressors but I swapped the 4 wires connectors to the EXV's, circuit 1 ran with its EXV controlled by circuit 2 and #1 did not trip, circuit 2 failed after 20 seconds.

  5. #18
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    Quote Originally Posted by GOVHVAC View Post
    Yep that's what I'm talking about, there's some other seals also if I remember correct that can cause similar problems. I realize it's hard to believe but I had two chillers last year going off on low refrigerant temp, I went through everything on them until I called tech support and they forwarded my call to publeo, Co where the chillers are made. They talked me through it and sent me all the service bulletins to diagnose it. We even had a factory Trane tech come down and verify it.
    I'm not saying that the chiller your working on couldn't be something else, just sayin it's worth looking into. I would suggest giving tech support a call and tell them what's going on and see if they can send you the service bulletins.

    It makes pretty good sense really if you think about it. If the compressor is loaded and trying to pump a lot of gas and the exv is barely open its going to drop the suction pressure real low real fast which is why you get the low refrigerant temp alarm.
    I tried to call Trane today but they are hard to get ahold, Can't call pueblo directly, there is a protocol involving Trane supply and a 3 way call and I didnt want to bother with that. the lip seal repair kit doenst cost that much $$$, I may quote it along with fixing a small leak I found .

  6. #19
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    Jan 2011
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    Central, PA
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    105
    Quote Originally Posted by valdelocc View Post
    I ran both compressors but I swapped the 4 wires connectors to the EXV's, circuit 1 ran with its EXV controlled by circuit 2 and #1 did not trip, circuit 2 failed after 20 seconds.
    Gotcha, you confused me when you said you locked out circuit 2.

  7. #20
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    Mar 2009
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    Mid-Mo
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    Quote Originally Posted by jabeu View Post
    How would an expansion valve that is barely open throw a low refrigerant temp fault in 20 seconds?
    Less refer, less pressure. Lower pressure, lower temperature. You're talking a big compressor too......

  8. #21
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    Mixing oil and fire with a big spoon.
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    Quote Originally Posted by valdelocc View Post
    I tried to call Trane today but they are hard to get ahold, Can't call pueblo directly, there is a protocol involving Trane supply and a 3 way call and I didnt want to bother with that. the lip seal repair kit doenst cost that much $$$, I may quote it along with fixing a small leak I found .
    sure seems like a lot of work when several items haven't been verified (at least not posted on here). by the way, the 'lip seal issue' was only on certain vintage 100 nominal ton compressors which aren't on this machine.
    "Mother" is the name for God on the lips and hearts of children....The Crow

  9. #22
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    Oct 2007
    Location
    Southern Indiana
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    Have you watched the amps on the display at start up? It's pretty simple to see if you are starting loaded, if the amps are above 45% then your starting loaded. If there close to 45% then your problem is some where else. Keep us posted on what you find, it will be interesting to know since I take care of several RTAA chillers.

  10. #23
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    I'm 99% sure the unit is low on charge, found a leak and quoted the repairs,let you know how it ends.

  11. #24
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    Quote Originally Posted by jayguy View Post
    sure seems like a lot of work when several items haven't been verified (at least not posted on here). by the way, the 'lip seal issue' was only on certain vintage 100 nominal ton compressors which aren't on this machine.
    Not only is the lip seal issue on the 100 ton compressor, this chiller uses a GP compressor. The lip seal issue is on the intermediate compressor which is a completely different style compressor.

    The OP needs to disregard everything that is being said about the compressor loading too fast. That is on the 130 to 400 ton RTAA that uses the intermediate compressors. The 70 to 125 ton chillers use the GP compressor and they don't have this issue.

  12. #25
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    Oct 2007
    Location
    Southern Indiana
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    Quote Originally Posted by R123 View Post
    Not only is the lip seal issue on the 100 ton compressor, this chiller uses a GP compressor. The lip seal issue is on the intermediate compressor which is a completely different style compressor.

    The OP needs to disregard everything that is being said about the compressor loading too fast. That is on the 130 to 400 ton RTAA that uses the intermediate compressors. The 70 to 125 ton chillers use the GP compressor and they don't have this issue.
    It's like I said before I'm not saying this is the only possible thing it could be. Obviously there are several things that can cause a Low Refrigerant Temp alarm. How hard is it to watch the amps on start up to rule out a compressor problem. There are other things beside lip seal failure that can cause these screw compressors to start loaded, like a bad loader/unloader, slide valve wear, bearing wear. I'm just giving the OP another area of concern to look into, it takes less than two minutes to watch the amps on start up to see whether its above 45% FLA, if it's not then you've ruled out a compressor problem.
    In my experience a low refrigerant charge won't cause this chiller to trip low refrigerant temp in less than 20 seconds, unless it is grossly undercharged. You said you had a clear sight glass.

  13. #26
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    Quote Originally Posted by GOVHVAC View Post
    It's like I said before I'm not saying this is the only possible thing it could be. Obviously there are several things that can cause a Low Refrigerant Temp alarm. How hard is it to watch the amps on start up to rule out a compressor problem. There are other things beside lip seal failure that can cause these screw compressors to start loaded, like a bad loader/unloader, slide valve wear, bearing wear. I'm just giving the OP another area of concern to look into, it takes less than two minutes to watch the amps on start up to see whether its above 45% FLA, if it's not then you've ruled out a compressor problem.
    In my experience a low refrigerant charge won't cause this chiller to trip low refrigerant temp in less than 20 seconds, unless it is grossly undercharged. You said you had a clear sight glass.
    I just wanted to make sure the op doesn't jump to buying a lip seal kit (as he stated) and spending a lot of time troubleshooting a loaded start problem. Yes I agree that he should take a few minutes to check the amp draw on startup and check the load / unload solonoids. The GP compressor doesn't have a slide valve. It has an unloader valve that modulates over ports. This design compressor doesn't have the issues that the intermediate compressor has that we are all so familiar with.

    I would concentrate on checking that the EXV is working properly and checking the sat evap and compressor suction temp sensors.

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