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  1. #1
    Join Date
    Apr 2005
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    Trane SWUD units

    This is driving me crazy. I have 14 swud units in a 450,000 sq. ft office building. 14 floors. Outside temp is 44 with a low outside humidity. Some units are in econo some are using one compressor. I have the the supply water temp at 62 degrees with the return running 65. I have lowered the supply to 55 but still have some that will stay in econo. Looking at the setpoints everything looks like they are set up the same. Why are they not all running in economizer, the floor heat loads are close. Tks!

  2. #2
    Join Date
    Jun 2007
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    Compressors lockout at inlet water temp of 54. (Typically).

    And sometimes economizer coil gets clogged/scaled etc and wont keep up.

    If econ can keep up it will not bring on a compressor(s).

  3. #3
    Join Date
    Apr 2017
    Location
    The Deep South
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    Quote Originally Posted by energyStarBoy View Post
    Compressors lockout at inlet water temp of 54. (Typically).

    And sometimes economizer coil gets clogged/scaled etc and wont keep up.

    If econ can keep up it will not bring on a compressor(s).
    Correct answer. On those units with a compressor running, the economizer isn't making setpoint. Time to clean the economizer or check for water flow issues at those units.

  4. #4
    Join Date
    Apr 2005
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    Thread Starter
    Ok, I get it, so I would need to increase lock out temp say from 54, and that is correct, they are set for 54, so I would raise to 58, 60 depending on outside temp to keep compressors off. The coils are well taken care of, good water treatment, brush tubes once a year. I am trying to do this for energy savings cost.
    Thank you much for your reply's!

  5. #5
    Join Date
    Apr 2017
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    The Deep South
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    Quote Originally Posted by buildingengineer View Post
    Ok, I get it, so I would need to increase lock out temp say from 54, and that is correct, they are set for 54, so I would raise to 58, 60 depending on outside temp to keep compressors off. The coils are well taken care of, good water treatment, brush tubes once a year. I am trying to do this for energy savings cost.
    Thank you much for your reply's!
    NO. There is a reason that the setting is for 54 degs. Something is preventing your economizers from keeping up on those SWUDs. You either have dirty economizers or the load is too great.

    Let the controls do what they do and find the reasons that the economizer isn't keeping up on those zones. Raising the compressor threshold is just a band-aid that won't fix your problem.

  6. #6
    Join Date
    Apr 2005
    Posts
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    Thread Starter
    Humm, I have two pumps on the roof which had vsd's added after the fact, maybe not enough flow?

  7. #7
    Join Date
    Sep 2007
    Location
    edmonds wa
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    Hopefully someone balanced them when they were installed, if no verification, that would be a good place to start along with having the econos checked.
    UA Local 32 retired as of Jan 2020

  8. #8
    Join Date
    May 2018
    Location
    VA/DC
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    the best thing we did was rip out the trane controllers and replace them with our own.

    lots of good comments as to why the econos may not be keeping up

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