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  1. #1
    Join Date
    Oct 2014
    Location
    Lebanon PA
    Posts
    28
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    Heat pump pulling into a vacuum in cooling mode

    A brand new heat pump heated great all winter long. Got a call in a/c mode unit trips out on low pressure. Put gauges on it and in cooling mode the low side pulls down until the switch opens. 5 psi. Any ideas? It's acting like a restriction

  2. #2
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    1,575
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    Sounds like a restriction in the cooling mode. What is the date code on this brand new heat pump.

  3. #3
    Join Date
    Oct 2014
    Location
    Lebanon PA
    Posts
    28
    Post Likes
    2014

  4. #4
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    8,512
    Post Likes
    Does it have a txv for the metering device in cooling mode? Does it have a copeland compressor?

  5. #5
    Join Date
    Nov 2007
    Location
    Tucson, AZ
    Posts
    200
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    might be the txv power head causing it to act closed. start there

  6. #6
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    1,575
    Post Likes
    Might be the Copeland rust additive/ txv problem.

  7. #7
    Join Date
    Jul 2013
    Location
    Richmond, VA
    Posts
    1,386
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    What about heat mode? Is it cool enough to run in heat mode?

    Make/model?

  8. #8
    Join Date
    Oct 2013
    Posts
    219
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    Brand new... dumb question but are the king(service) valves backed out to the left all the way?

  9. #9
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
    1,575
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    You did not mention a brand, but your distributor will know if that unit is in the date range of the txv clogging up issue. Or at least fill you in on the date ranges and what models are affected. also a lot of info on here about that issue.

  10. #10
    Join Date
    Jan 2012
    Location
    San Gabriel Valley
    Posts
    15
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    Heat pump refrigerant circuitry can get confusing, so start with obvious and easiest, I agree with N2fords, make sure the sensing bulb is installed correctly and insulated, if it is then remove it and dunk it in hot water while operating, see if it opens up. Check for icing directly after txv, could be dibree stuck in the orrifice, which would be getting bypassed in heat mode.

  11. #11
    Join Date
    Oct 2014
    Location
    Lebanon PA
    Posts
    28
    Post Likes
    It has a txv in both indoor and outdoor. It's a Gibson unit.

  12. #12
    Join Date
    Jan 2012
    Location
    San Gabriel Valley
    Posts
    15
    Post Likes
    Wow, never seen txv for outdoor in a split system. Well the one outdoor should be bypassing durring cooling, so unless it was clogged, but then I don't think it would heat verry well, start checking line temps for temp drops, see if the liquid line is cooler than ambient, it should be just above ambient, if it's cooler then there's a restriction somewhere before that point of measurement. While running try disconnecting and reconnecting reversing valve several times with about 5 seconds in between, maybe it's stuck or something is stuck somewhere.

  13. #13
    Join Date
    Mar 2015
    Location
    ARK.
    Posts
    225
    Post Likes
    TXV's are very popular on the higher eff units starting at 12's.
    Trane & Rheem both do.

    Possible fried sens bulb on the coil suction line also. SEE this a lot.
    "Wet rag?,WE don't need no stinking wet rag."

    Look for frosting when in operation first as this is a dead give away before you get "all into it".

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