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  1. #27
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,591
    Quote Originally Posted by daviddsims View Post
    Took another look today and sure enough it had a txv on the evaporator. I added a small amount of refrigerant to try and get to 10 degrees subcooling. Getting about a 15 degree split out of the evaporator.
    What are you readings now.
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  2. #28
    Join Date
    Mar 2008
    Location
    West Monroe, LA
    Posts
    67
    SP=82
    DP=255
    SL temp=65
    LL temp=110

    Still not completely happy with the results.

  3. #29
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,591
    8SC. Dirty coil maybe.
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  4. #30
    Join Date
    Oct 2010
    Location
    AZ
    Posts
    627
    Is this a heat pump? If so, measure the rise in temp of the lines across the reversing valve to make sure it is not leaking.

    Where are you measuring the suction line temp? is this as close to the evap as possible. and measuring LL as close to condenser as possible?

  5. #31
    Join Date
    Mar 2008
    Location
    West Monroe, LA
    Posts
    67
    No it is not a heat pump. I measured superheat at the outdoor unit and subcooling at the outdoor unit.

  6. #32
    Join Date
    Oct 2010
    Location
    AZ
    Posts
    627
    Quote Originally Posted by daviddsims View Post
    No it is not a heat pump. I measured superheat at the outdoor unit and subcooling at the outdoor unit.
    Superheat at the outdoor unit really doesn't tell you much. You should measure it as close to the evaporator as possible.

  7. #33
    Join Date
    Jul 2005
    Posts
    5,292
    Quote Originally Posted by dijit View Post
    Superheat at the outdoor unit really doesn't tell you much. You should measure it as close to the evaporator as possible.
    Yep, there's quite a difference on mine. About a 6 rise in line temp from evap to compressor. Figuring in pressure drop that gives me about a 7 difference in SH. It's about 103 outside right now and my line set runs through the attic.

  8. #34
    Join Date
    Mar 2008
    Location
    West Monroe, LA
    Posts
    67
    Yeah I should have taken it at the evap as it does run through the attic and it is 103 here as well.

  9. #35
    Join Date
    Jul 2000
    Location
    NW IL.
    Posts
    3,935
    Get in the habit of measuring SL and LL temperatures at condensing unit and at evaporator. It will reveal lineset problems.
    Aircraft Mechanical Accessories Technician. The Air Force changed the job title to Air Craft Environmental Systems Technician. But I've decided I'll always be a Mech Acc.

  10. #36
    Join Date
    Mar 2008
    Location
    West Monroe, LA
    Posts
    67
    So what is the consensus on this unit? Even adding refrigerant having trouble getting to the 10 degree subcooling on this unit?

  11. #37
    Join Date
    Jul 2005
    Posts
    5,292
    Quote Originally Posted by daviddsims View Post
    So what is the consensus on this unit? Even adding refrigerant having trouble getting to the 10 degree subcooling on this unit?
    You didn't add enough.

  12. #38
    Join Date
    Jul 2000
    Location
    NW IL.
    Posts
    3,935
    Quote Originally Posted by daviddsims View Post
    So what is the consensus on this unit? Even adding refrigerant having trouble getting to the 10 degree subcooling on this unit?
    What is the LL approach temperature? Liquid Line temperature - Ambient temperature if it is pushing 10 degrees may be a dirty condenser coil. If coil is clean it may be non condensables.
    Aircraft Mechanical Accessories Technician. The Air Force changed the job title to Air Craft Environmental Systems Technician. But I've decided I'll always be a Mech Acc.

  13. #39
    Join Date
    Mar 2008
    Location
    West Monroe, LA
    Posts
    67
    The outdoor unit has superheat charging chart so I used my Fieldpiece HG3 to get a 12 target subcool. Tell me about LL temp - outdoor rule you referenced?

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