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  1. #1
    Join Date
    Jul 2010
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    13

    Question Trane chiller - 1U12 help

    I have a trance chiller model CGACD1554EFNMM63FGHPRTW operating with the Honeywell w7900 (1U12).

    2 - semi hemetic compressors.
    Air cooled.

    I recently acquired this wonderful friendly unit.

    The issue I seem to be experiencing is that the 1U12 isn't calling in for the 3rd stage on both compressors.

    Prior to that the water leaving sensor was changed with a new one and has heat transfer co Lund to make sure proper temp is read.

    The sensor was also ohmed out. It's reading properly.

    My main question is, does anyone think that it would be ok to piggy back the 3rd stages off the 2nd stages?

    I observed the following on start up -

    1U12 lights second LED stating start up.
    After time delay -
    Stage 1 on compressor 1 comes on.
    Compressor runes for so long, then condenser fan runs.
    Stage 1 on compressor 1 starts up.
    10-15 seconds later, stage 2 on compressor 1 activates.
    10-15 seconds after, stage 2 on compressor 2 activates.

    Stage 3 never activates on either compressor.

    Water entering temp is roughly 70-72 degrees (bad gauges)
    Water leaving temp is roughly 65 degrees according to gauge.

    Ambient temp is 85.4F

    Pump return pressure reads 18measily psi
    Pump supply pressure reads 33psi.

    There's no flow meters either.
    Couldn't honestly say I know what's the current gpm.

    Pressures last checked were relatively good.

    I hope my information is helpful to an extent.

  2. #2
    Join Date
    Mar 2004
    Location
    ottawa canada
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    Is the controller set for 6 stage control ??
    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 .

  3. #3
    Join Date
    Oct 2009
    Location
    USA
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    48
    Make sure the controller is set for the proper number of total stages. Also make sure there isnt a load limit t-stat preventing the last stages from comming on. This stat should be on the return water.

  4. #4
    Join Date
    Jul 2010
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    The controller is set for 6 stages.
    Water temp out is at 45
    And delta T at 10.

    I'm going to look for that load limit t-stat on the return.

  5. #5
    Join Date
    Mar 2005
    Location
    Indiana
    Posts
    147
    The load limit is built in to that control. It will not load up all stages until water is below 61 or 62 degrees.

  6. #6
    Join Date
    Aug 2011
    Location
    San Jose California
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    153
    just a thought if you can.. get a 55 gallon barrel and see how long it takes to fill. if you have a bypass installed you could get gpm +-
    Our fate is ours alone to decide as long as we remain armed heavily enough to dictate it.

  7. #7
    Join Date
    Sep 2008
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    A land down under
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    It has been a while since working on recip chiller product but I beleive the load limit feature of the Honeywell Controller will prevent loading until LWT falls below 55F (13c), on increasing water temperature load limit operation is initiated at 64F (18c).
    Necessity is the mother of invention

  8. #8
    Join Date
    Dec 2009
    Location
    Southern US
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    504
    This may not be the case but it is worth mentioning IMO.

    Have you checked the sensor to be sure its reading correctly to the leaving water temperature? Also I have run across W7100's that even when the sensor read correctly the controller did not stage properly and had to be set lower to compensate. If that is the case I would not leave in this condition on a water cooled system for obvious reasons.
    I'm good at making things cold...You can ask my first two wives!

  9. #9
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    Quote Originally Posted by freonr22 View Post
    just a thought if you can.. get a 55 gallon barrel and see how long it takes to fill. if you have a bypass installed you could get gpm +-
    what? they are supposed to break open the chilled water lines and let them dump into a 55 gallon bucket and time it with a stop watch? is this what you mean?

    a CGACD155... has a minimum flow rate of 144 gpm to 240 gpm depending on the evaporator barrel (at 144 gpm, 55 gallons that is 23 seconds). the maximum water flow (again, depending on the evaporator barrel) is 700 gpm which is approximately 4.7 seconds...gotta be quick to shuf off the pump i guess!

    of course, without any head pressure, the pump gpm could triple its output or more.

    Load Limit is de-energized at 56F when the leaving water temperature is falling and it is energized at 64F when the leaving water temperature is rising.

    The number of stages is supposed to be fixed at the factory (changing the knob doesn't do anything).

    i do not recommend jumping out your stages. this will cause instability, short cycling and possible low pressure lockout conditions. i think that it might be ok for TESTING PURPOSES ONLY. but i would not recommend leaving it that way.
    It's tube brushing season...93% done (39.35 miles of tubing)...only 1,242 tubes to go!

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  10. #10
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    Quote Originally Posted by freonr22 View Post
    just a thought if you can.. get a 55 gallon barrel and see how long it takes to fill. if you have a bypass installed you could get gpm +-
    What???????

  11. #11
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    Quote Originally Posted by R123 View Post
    What???????
    that's what i said!!
    It's tube brushing season...93% done (39.35 miles of tubing)...only 1,242 tubes to go!

    Original member of the Raccoon Brotherhood.

    EVERYTHING IS AWESOME!!!

  12. #12
    Join Date
    Jul 2007
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    Quote Originally Posted by jayguy View Post
    that's what i said!!
    Like you said, if he completely cut the CHW line open and attached a large diam fire hose to dump into a drum, there would be no head and the flow would be alot higher than it would be flowing through a closed loop system with back pressure.

    Plus he would pump all the water out of the system and run the pump dry.

  13. #13
    Join Date
    Mar 2004
    Location
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    Quote Originally Posted by freonr22 View Post
    just a thought if you can.. get a 55 gallon barrel and see how long it takes to fill. if you have a bypass installed you could get gpm +-
    I got a 2500 ton Duplex for you to check the flow on with your 55 gal barrel and Im gonna sell tickets to the show !!!!!!!!
    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 .

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