Chiller Load
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Thread: Chiller Load

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  1. #1
    Join Date
    Jul 2009
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    Chiller Load

    Want to hear your opinions on chillers running with low load and cycling. I have a Trane cvhf 500ton chiller that runs 85% of the time @ 20% and with cooler fall temps it has started cycling off and on. The chilled water stpt is 50 and I moved the dead band from +-3 to +-5 this helped the cycling some. Over the weekend the compressor started 22 times in the span of about 2 hours. I talked to a guy at Trane he was concerned by this, the management here is not. In your opinion should I really push this issue to have it resolved or do you think the chiller will fare fine. Any increase load is most likely not going to happen until spring.

    On a side note any way to eak out load from the AHU's there are 6 running @ 30% maintaining a room temp of 55 degrees. Was thinking about moving the set point on 3 of them to 58 to make the other 3 work a little harder?

  2. #2
    Join Date
    Nov 2008
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    359
    What year is this chiller. The manf. date is the first set of #'s after the L at the beginning of the Serial #.

    Also what panel is on the chiller.

    22 starts in 2 hours seem very high and would be hard to achive on alot of panels.

  3. #3
    Join Date
    Oct 2001
    Posts
    6,932
    every 5 minutes it restarts where is the restart inhibate program.for the peak demand your getting slammed with on a those resstarts you could slide inn a 100 ton scroll chiller to catch the night/fall mode.how about installing a dry cooler in series with the evap barrel or add a barrel in the MER and run the tower thru it....anyhing to keep that main chiller off.
    "when in doubt...jump it out" http://www.youtube.com/watch?v=U1qEZHhJubY

  4. #4
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    Jul 2009
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    Year 2009
    Tracer adaptiview control

  5. #5
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    1,997
    So it is under warranty ,so yes you should be concerned about it. Obviously whoever set up the adaptiview didnt do it right to prevent short cycling .
    I would get whoever did the start up to check the way the controller is set up to check all the settings in the adaptiview.
    Is it comfort cooling or process?
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  6. #6
    Join Date
    Jul 2009
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    It is a raised data center floor. So I guess comfort cooling. The installer looked at it and the only suggestion he could make was turning up the deadband. The only thing that did was keep it off for a few extra minutes. Today the oil heater went out on it wonder if that was a cause of the cycling or something else?

  7. #7
    Join Date
    Nov 2008
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    359
    I guess that we could get into a long discussion on the design criteria, hot gas and what not.
    Does this machine have a Freq. Drive.
    A typical machine will turn down to about 10%. If it is a 10 degree drop machine ie... 55in 45 out it will unload down to about a one degree drop. Which for a nominal CVHF500 is probably around 50 ton.
    If you have less load than that the machine has no choice but to cycle.
    You may have a problem on your hands.

  8. #8
    Join Date
    Jul 2009
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    10
    I tend to see a 1degree drop running at 10% the chiller shuts down on what I assume is the min load timer. Well hopefully when the install co comes out to fix the oil heater they will give me some fire to go the the managment with. Or that we get some load soon.

  9. #9
    Join Date
    Apr 2009
    Location
    In the south
    Posts
    30
    They should be concerned. Starting and stopping like that is not good and if you lose the motor it may not be covered under the warranty because of the way it is being run. Next thing is who set it up. Min run time is usually set at 30 min. and who figured the load. There should have been a pony chiller installed for such small loads.

  10. #10
    Join Date
    Jul 2009
    Posts
    10
    Quote Originally Posted by Tranetek View Post
    They should be concerned. Starting and stopping like that is not good and if you lose the motor it may not be covered under the warranty because of the way it is being run. Next thing is who set it up. Min run time is usually set at 30 min. and who figured the load. There should have been a pony chiller installed for such small loads.
    I think the original plan called for much more load then after we had the building running the customer pulled out. I did finally find the min load timer and it was set for 30 mins.

  11. #11
    Join Date
    May 2001
    Location
    Western Wa
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    1,817
    I wonder if the oil took off, and maybe that was the cause of the oil heater failure.

    If nothing else, figure out how warm of water you can tolerate before the sh** hits the fan, and set the deadband accordingly. And that's a Mickey Mouse band-aid for some piss poor engineering.

    You'll be spending a lot of money on parts when the warranty runs out.
    God Bless our Veterans

    God Bless the USA

  12. #12
    Join Date
    Mar 2004
    Location
    ottawa canada
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    1,997
    Whats your minimum capacity start point % setting ?? What are your differential to start/stop settings .
    Is the soft loading feature enabled ??
    The 64 roars to life Whoo hoo ...shes a rolling chassis .
    You bend em" I"ll mend em" !!!!!!!
    I"m not a service tech.. I"m a thermodynamic transfer analyst & strategic system sustainability specialist
    Best Austin Healey In Show twice in 2013 .....All those hrs paid off .

  13. #13
    Join Date
    Oct 2006
    Location
    Central Texas
    Posts
    625
    Drop the setpoint down 2 or 3*, UCP2 or CH530 panel? Soft load needs to be enabled. Set it up for Return water reset. Ex. 10* Delta no reset, 2* Delta full reset, w/ maybe 5* increments. Micro will monitor the delta t, increase setoint by x depending on parameters set. This will help slow down short cycling & keep machine running. I've got an account with several chillers on different buildings 2-pipe systems. All set up on reset, helps tremendously in cooler weather and low load conditions. May not solve all your problems, but I'd give it a shot. Hope this can help.
    Sic Semper Tyrannis.

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