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  1. #1
    Join Date
    Oct 2010
    Location
    michigan
    Posts
    20

    Trane RTAA 100ton

    Package chiller tripping on low pressure latch fault. actual suction while monitoring is 60Psig and display is reading about the same. Discharge pressure running around 225-250.
    2nd stage runs like a champ after stage 1 trips out, so ive ruled out a flow issue...water temp running at 47 degrees. flow switch is working as it should....At this point im looking for ideas whether u think its the pressure switch near the barrel going bad or if exv is closing/not opening as it should.

  2. #2
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,440
    make sure that the diagnostic really is: Low Pressure Cutout - Ckt 1

    if the diagnostic is different, then it could be something else otherwise monitor the low pressure switch (voltage side) while watching your gages to find out for sure.
    How to make the perfect "Half-Hitch" knot or any other boyscout knot in 3 easy steps...

    1. Remove your meter leads from the meter and very carefully return them to their storage case or bag.
    2. Wait 2 seconds
    3. Very carefully remove your meter leads from their storage place and enjoy your new knot!

  3. #3
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,332
    Quote Originally Posted by jayguy View Post
    make sure that the diagnostic really is: Low Pressure Cutout - Ckt 1

    if the diagnostic is different, then it could be something else otherwise monitor the low pressure switch (voltage side) while watching your gages to find out for sure.
    X2

    Post the exact alarm the chillers calling out. There are other similar alarms that mean different things.

  4. #4
    Join Date
    Oct 2010
    Location
    michigan
    Posts
    20
    Monitored unit today and was tripped on low pressure again... checked pressures and was running 60 and 230 at 50 degree water temp. Superheat was 6 degrees and subcooling was 20. Going to change pressure switch near the barrell and gk from there unless you guys have any other input?

  5. #5
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,332
    Your not going to post the exact alarm?

  6. #6
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,440
    Quote Originally Posted by philbilly88 View Post
    Monitored unit today and was tripped on low pressure again... checked pressures and was running 60 and 230 at 50 degree water temp...
    you WATCHED it trip with those pressures or...it tripped....and then later, after you reset it, you had those pressures?
    How to make the perfect "Half-Hitch" knot or any other boyscout knot in 3 easy steps...

    1. Remove your meter leads from the meter and very carefully return them to their storage case or bag.
    2. Wait 2 seconds
    3. Very carefully remove your meter leads from their storage place and enjoy your new knot!

  7. #7
    Join Date
    Mar 2005
    Location
    Indiana
    Posts
    159
    We use to get that alot on those chillers, just replace the switch. If you take it off and test it, it is probably opening higher than it should.

  8. #8
    Join Date
    Oct 2010
    Location
    michigan
    Posts
    20
    r123 the alarm was low pressure cutout...it was a latch fault alarm.

    jayguy i reset the chiller and minutes later it alarmed again...then i reset it hooked up my gauges, put comp. 1 in test mode, thats when i checked pressures, superheat, and subcooling. The compressor did not trip after that.

  9. #9
    Join Date
    Jul 2013
    Location
    Florida
    Posts
    19
    RTAA does not have a transducer. It shuts down on low pressure if the low pressure switch is tripped. If it is tripping on low pressure but you feel that pressure is adequate then I would suggest investigating/replacing low pressure switch. When you were measuring the pressures what percentage was the unit running at? It needs to be near fully loaded.

  10. #10
    Join Date
    Oct 2010
    Posts
    28
    looks like it you have bad switch,switch open up at 7lbs 4(this is from the rtaa IOM) if you need a copy let me know.


    Compressor Discharge High Pressure
    Switch PSIG
    300 20 405 7
    Compressor Motor Winding
    Thermostat F
    181 221
    Low Pressure Cutout 22 4 7 4
    Attached Images Attached Images

  11. #11
    Join Date
    Jul 2013
    Location
    Florida
    Posts
    19
    btw: The pressures displayed on the screen are calculated pressures based on temperature and various other items on the RTAA.

  12. #12
    Join Date
    May 2011
    Location
    NC Foothills
    Posts
    73
    Run the EXV test as well. Make sure it passes that.

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