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  1. #14
    Join Date
    Jan 2008
    Posts
    40
    He cleaned the condenser coil. The evap was clean (I'm careful about my filter maintenance!)

    -cinergi

  2. #15
    Join Date
    Apr 2002
    Location
    Omaha, NE
    Posts
    1,561
    OK, guys. Here's what I don't understand: it sounds like the system was building up head pressure and eventually the internal relief valve was venting back to suction side. This would continue until the internal overload in the compressor would finally kick out. After cooling off awhile, it would reset. My question is this: how would a bad TXV cause this to happen? Why wouldn't it just pump down, and cut out on low suction pressure? Or just continue to run into a vacuum? Why the excess head pressure?

  3. #16
    Join Date
    Apr 2002
    Location
    Omaha, NE
    Posts
    1,561
    Or... is the TXV somehow sticking wide-open and causing the high head??

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,774
    Condenser may not be able to hold the entire operating charge.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  5. #18
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    TXV could be hunting severly. Causing a constant change in pressures and temps.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  6. #19
    Join Date
    Mar 2003
    Posts
    7,314
    many resi units do not have low presssure switches.

  7. #20
    Join Date
    Apr 2002
    Location
    Omaha, NE
    Posts
    1,561
    Quote Originally Posted by flange View Post
    many resi units do not have low presssure switches.
    So where is all the heat coming from to elevate the Head pressure? If the low side is into vacuum it's not moving any heat from the evap. coil. All the refrigerant is stacked in the condenser and liquid line, being cooled down to ambient. Is it possible that the high compression ratios and the heat of compression are responsible for all the excessive head pressure? I've never witnessed a system running long term into a vacuum with no LPCO to know the effects this has.

  8. #21
    Join Date
    Apr 2002
    Location
    Omaha, NE
    Posts
    1,561
    Quote Originally Posted by beenthere View Post
    Condenser may not be able to hold the entire operating charge.
    I didn't know it was possible for a properly charged system not to have enough liquid "storage" capacity so that it couldn't be pumped down. Is this true?

  9. #22
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,774
    Depends on line set and indoor coil match.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  10. #23
    Join Date
    Jun 2008
    Location
    Surrey, BC, Canada
    Posts
    35
    I wonder if it's a R410A unit. With R22 I hardly ever ran into a TXV problem. Seems like more frequent failures with the R410A.

  11. #24
    Join Date
    Jan 2008
    Posts
    40
    It's an R-22 system, circa 1996. The tech said the same thing: he rarely has problems with the R-22 systems, but often replaces various sealed-system parts on the R-410 units because of the higher pressures.

    -cinergi

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