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  1. #1
    Join Date
    Dec 2003
    Posts
    148

    RTAC Pumpdown Terminated

    The other day I went to stop a RTAC250 to do an inspection. As circuit #1 was shutting down I got a diagnostic “Pumpdown Terminated.” In checking the IOM I was left a little bewildered. The explanation is somewhat vague. What are the “specific set of diagnostic criteria?”
    I know that below 50*F OAT these machines do what is called an “Operational Pumpdown.” The explanation on that in the IOM seems to be incomplete. I even checked the latest and greatest IOM on Trane’s website and the explanations are exactly the same as my original IOM that came in the unit. This particular unit is a 2009 with version 30.0 software.
    Unfortunately, I was not on the Refrigerant Screen to see what the pressures or liquid level were doing at the time. I was hoping that maybe you Trane guys or RTAC experts could shed a little light on these explanations.


    From the IOM-----
    Operational Pumpdown:
    The circuit is in the process shutting down by performing an operational pumpdown just prior to stopping the last running compressor. The EXV is commanded closed. Pumpdown will terminate when both the liquid level and the evap pressure (where's the rest????)

    Pumpdown Terminated - Circuit 1:
    The pumpdown cycle for this circuit was terminated abnormally due to excessive time or due to a specific set of diagnostic criteria - but w/o associated latching diagnostics

    I appreciate any help.
    Still learning....

  2. #2
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,336
    what?! that's not a good enough explanation for you?

    operational pump down automatically stops the compressor when the suction pressure reaches 5 psig. if the compressor runs for 2 minutes before reaching 5 psig, then you get the warning. if there is another diagnostic that occurs (like some other issue like high pressure cutout or something), then the pump down will also stop.
    "Mother" is the name for God on the lips and hearts of children....The Crow

  3. #3
    Join Date
    Dec 2003
    Posts
    148
    Thanks Jay,

    I kind of assumed it would be around 5psi, I think I remember reading somewhere that the service pumpdown terminates at 5psi. I'm still wondering, does the Operational Pumpdown want to see 5psi and a -1 liquid level? I can't figure out why they make reference to liquid level and evap pressure.
    Still learning....

  4. #4
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,336
    Quote Originally Posted by agross View Post
    ...does the Operational Pumpdown want to see 5psi and a -1 liquid level? I can't figure out why they make reference to liquid level and evap pressure.
    i am not sure why (for sure) but if you are at 5 psig with R134a, the saturated temperature would be -3.05F...if you have a liquid level then you have issues. they may only want both as a double check that all is working ok which makes sense.

    if you have a real liquid level and a fake 5 psig then you have a faulty pressure transducer. if you really have 5 psig but you also have a fake liquid level, then you have a faulty liquid level sensor.

    maybe? i don't know for sure but it makes sense to me since, pretty much no matter what, you should have both during pump down.
    "Mother" is the name for God on the lips and hearts of children....The Crow

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