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  1. #1
    Join Date
    Jun 2012
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    6

    Trane rtaa low evap temp alarm

    I have a trane rtaa 125 chiller. Both compressors trip on same alarm. Starts up in 2 min the female loader in energized then the suction psi drops has well as the low suction temp set point witch is set to default 22 degress. No glycol in chiller. 11 degrees sub cooling with clear site glass. All 5 fans running 80+ degress ambient temp. 7 to 10 psi differential on entering and leaving water flow. Sometime might run all day other time trips within 3 min of start. Thinking bad suction evap sensor ?????? Any suggestion please

  2. #2
    Join Date
    Apr 2012
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    Both circuits sounds like low water flow.

  3. #3
    Join Date
    Jun 2012
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    6
    Sorry alarm is low suction evap alarm

  4. #4
    Join Date
    Jun 2012
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    6
    Even though I have a diferential and flow switch is made. Theres about 10 other rtaas on location with same installs piping pumps etc.... Could loaders be possible or looking to deep into it

  5. #5
    Join Date
    Apr 2012
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    They're notorious for eating sensors but if I were you I would do my due diligence and make sure I have at least minimum flow,

    Yes condemning unloader solenoids is a bit premature.

  6. #6
    Join Date
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    Minimum flow on that chiller is 150 GPM.

    If you're only getting a 7 psi diff. then you're close to the minimum GPM

  7. #7
    Join Date
    Jun 2012
    Posts
    6
    Should the diff be greater. What is recomened for theses rtaas. Gonna check strainers on pumps tomorrow. Someone prior changed one sat suction temp sensor on circuit 1. I was told they come as a pair with the suction temp sensor. Have you ever seen the board giving the wrong pulse signal to the loaders or is that rediculous.

  8. #8
    Join Date
    Apr 2012
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    The pair is the suction temp sensor ( located at the back of the compressor ) and the suction saturation sensor ( located after the EEV ) per circuit. SSH measurement


    So if you change them you will have 4 sensors to change out.

    As far as your flow there is a chart on that chiller that you can access online.

    Typically I don't usually trust the mounted gauges if there installed and use my one trusty gauge I keep on my truck to get accurate measurements.

    It may be sensors but both circuits bringing up low evap. sensor alarms on the same Chiller would justify a look at actual GPM.

  9. #9
    Join Date
    Mar 2004
    Location
    ottawa canada
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    2,029
    Duhhhhhh if there both tripping it aint the sensors , check the common denominator ............Flow !!!!!!!!!!!!!!!!!!!!!!!
    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 .

  10. #10
    Join Date
    Apr 2012
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    Paper Street Soap Company
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    Quote Originally Posted by Healey Nut View Post
    Duhhhhhh if there both tripping it aint the sensors , check the common denominator ............Flow !!!!!!!!!!!!!!!!!!!!!!!
    Healey Nut what are the models of the two Austin Healeys in your avatar.

    There is a guy locally that sports around in a yellow frog eyed sprite.

  11. #11
    Join Date
    Mar 2004
    Location
    ottawa canada
    Posts
    2,029
    Red one ...64 3000 Mk 3 BJ8
    Green one ...67 3000 Mk3 BJ8
    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 .

  12. #12
    Join Date
    Apr 2012
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    Paper Street Soap Company
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    Quote Originally Posted by Healey Nut View Post
    Red one ...64 3000 Mk 3 BJ8
    Green one ...67 3000 Mk3 BJ8
    Did you do the restoration or did you acquire them in that shape ?

    Are they hard to find parts for ?

  13. #13
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,594
    Just because a flow switch is "made" doesn't ensure that there is water flow or sufficient water flow. Differential pressure switches aren't the most accurate things either. Proper flow switch adjustment sometimes requires some time and effort to get just right. Use the same pressure gauge when checking for pressure drop, there is a formula to tell you gpm. Get your post count up and apply for the pro membership, them you can have access to more information than you can possibly absorb.

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