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  1. #1
    Join Date
    Jul 2010
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    Denver, CO
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    TXV Powerhead Lost Charged

    I have a chiller and I believe that one of the circuits has a failed powerhead on the TXV but I am not 100% on this diagnosis.
    About 2 months ago I removed the filter dryer and replaced it and charged the system to the manufacturers specs. Today I found this compressor locked out on a low pressure alarm. I reset the alarm and the compressor ran less than 5 seconds. In that time the suction pressure dropped to 25 psi (its a R22 system) and the head pressure rose to 200 psi. This leads me to think that the TXV powerhead lost its charge and is more or less working like a pump down solenoid. Am I missing something here or am I correct in my diagnosis?

  2. #2
    Join Date
    Apr 2012
    Location
    winnipeg
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    1,330
    could be.. may be valve itself... are you sure its got enough refrigerant.. is there any liquid line solenoids...
    it was working.... played with it.... now its broke.... whats the going hourly rate for HVAC repair

  3. #3
    Join Date
    Jul 2010
    Location
    Denver, CO
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    433
    There are no LLSV. I am not positive on the charge, it just seems like a lot to lose in a short period, not impossible. I have leak checked it with an electronic leak detector and got not hits. I will find out if it has enough once I pull the charge, I am just leaning towards the TXV. What in the valve would cause it to act this way?

  4. #4
    Join Date
    Apr 2012
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    Paper Street Soap Company
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    It could be. It could be the valve itself, or a liquid solenoid valve. Is there icing on the leaving side of the TXV ??

    That would pretty much tell you where the restriction is.

  5. #5
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    Jul 2010
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    5 seconds of run time doesn't allow for much icing, or diagnostics for that matter.

  6. #6
    Join Date
    Apr 2012
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    Quote Originally Posted by HuNGRYTeCH View Post
    5 seconds of run time doesn't allow for much icing, or diagnostics for that matter.
    Pump it down and change it out if you suspect the power head. Usually when I lose a power head it pretty obvious. Like the cap line has a hole worn into it or its completley rusted away.

  7. #7
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
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    3,667
    Quote Originally Posted by HuNGRYTeCH View Post
    5 seconds of run time doesn't allow for much icing, or diagnostics for that matter.
    What does the suction pressure do when the compressor shuts down?
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  8. #8
    Join Date
    Sep 2008
    Location
    Western PA
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    24,940
    Quote Originally Posted by carmon
    could be.. may be valve itself... are you sure its got enough refrigerant.. is there any liquid line solenoids...
    I've replaced a heck of a lot more power elements than I have expansion valves.

    The symptoms sure sound like a bad element...

  9. #9
    Join Date
    Jul 2010
    Location
    Denver, CO
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    433
    I pulled the charge today, had the same amount I put in. Took off the power head and found a small pinhole in the diaphragm with my eye glass. I took apart the rest of the valve and found no debris. Put it back together, replaced the power head, charged it up, and now its running like a champ.

  10. #10
    Join Date
    May 2003
    Location
    Utah
    Posts
    689
    Certainly sounds like a restriction in the liquid line; whether a dead element keeping the TEV closed, a plugged filter-drier, etc.

    Once you remove the power head, take your thumb and attempt to push the disphragm in. If there' no charge (or a weak charge) you'll be able to move the diaphragm with your thumb.

    Also, when you screw the power head back onto the valve, you'll feel it come in contact with the pushrods and start to depress the pushrods during the last half turn or so.

    If you're seeing something different than this, then the power head has lost its charge.

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