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  1. #1
    Join Date
    Nov 2014
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    Philadelphia area
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    Split system high subcool/high superheat

    So i installed a 2.5 ton amana split system in a house last summer and at startup everything was running good. I got called out late in the season and had high subcooling and high superheat. (Sc: 20° and sh: around 25° 40° saturated and 65° at evap outlet). I tryed adjusting the TXV and it didnt change my readings too much. The condensing unit is about 30 feet below the air handler and the lineset is about 75 feet long. My thought is now that the pressure is dropping in the liquid line and flashing before it gets to the TXV. Has anyone ran into this problem before? And if so what was the solution? Adding charge till you start getting adequate superheat? I’m thinking about adding a sight glass but i feel ridiculous doing that on a 2.5 ton resi system lol. Any inout is appreciated as i am scheduled to go back in the spring time.

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
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    14,484
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    Pull the charge
    Weigh it
    Match it to the total charge.

  3. Likes DavidDeBord liked this post
  4. #3
    Join Date
    Nov 2014
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    Philadelphia area
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    Thread Starter
    If you are trying to see whether it’s undercharged then i would be curious why i had such high subcooling.

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  6. #4
    Join Date
    Jan 2017
    Location
    San Diego
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    Quote Originally Posted by Bglenn525 View Post
    If you are trying to see whether it’s undercharged then i would be curious why i had such high subcooling.
    Did you check the amps? See attached photo

    Sent from my LG-TP450 using Tapatalk

  7. #5
    Join Date
    Nov 2014
    Location
    Philadelphia area
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    Thread Starter
    Quote Originally Posted by Raehvac View Post
    Did you check the amps? See attached photo

    Sent from my LG-TP450 using Tapatalk
    the image attached does not work. also I believe amps are rated at around 10 and I was running around 6

  8. #6
    Join Date
    May 2006
    Location
    Philadelphia, PA
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    1,802
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    There is a LL restriction.
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

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  10. #7
    Join Date
    Sep 2007
    Location
    State College, PA
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    Did you pull the TXV sensing bulb and heat and cool it to see if there was a change?

    Most residential TXV's are not adjustable. Are you sure you adjusted it?
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  11. #8
    Join Date
    Sep 2007
    Location
    State College, PA
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    Quote Originally Posted by comfortdoc View Post
    There is a LL restriction.
    Sounds about right!
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  12. #9
    Join Date
    Dec 2006
    Location
    phoenix
    Posts
    286
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    Pulling the charge and weighing it will not help, it is a split not a package.
    30' up and 75' away, does the OEM allow this with this model? Model and line sizes would help.
    SC and SSH are close, it could just be the lineset length and height. Did you record the original info inside the CU electrical panel with magic marker? It may have been that way always.
    If the TXV is lacking a full liquid charge, you can feel or hear it at the TXV.
    Adding a little more juice will see if the SSH starts to drop. If adding juice lowers your SSH then it not the TXV.
    30' up will effect your press/SC/charge/etc.

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  14. #10
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
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    What was the recommended SC for that lineset length? You may be spot on charge wise. My mind would be wondering what your metering device is doing. I see attic temps of 140*+ all summer and they manage to cool just fine. If you’ve made sure that your air entering the coil is the same temp as the indoor air then measure for a temp drop across the drier, same from its exit to the metering device. If it’s good then most likely the txv needs a looking at. Wouldn’t be the first one to go bad. Nothing wrong with putting a SG on it as long as you don’t use it for charging. Think of it as a visible moisture tester.

  15. #11
    Join Date
    Feb 2018
    Location
    South Florida
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    Quote Originally Posted by comfortdoc View Post
    There is a LL restriction.
    Sounds like this. Did you use nitrogen when you brazed the linesets? Also, with that kind of vertical height, did you take into account any static pressure losses when figuring out your psi's and temps?

  16. #12
    Join Date
    Dec 2015
    Location
    Jacksonville fl
    Posts
    96
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    Are you taking the sh at the evap or condenser? That’s a long line set


    Sent from my iPhone using Tapatalk

  17. #13
    Join Date
    Jun 2012
    Posts
    38
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    LL restriction or bad txv. If warming txv bulb doesn't change pressures its the TXV. A restriction before txv will cause frosting at restriction. I've seen too many txv's that lost bulb pressure.

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