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Thread: Not cooling

  1. #1
    Join Date
    Mar 2012
    Location
    Grand Prairie, TX
    Posts
    27

    Not cooling

    I'm working on a 3 ton Trane ac system....bout 12 yrs old...
    The house is not cooling properly.
    83 degree outdoor
    Low side 74 psi, 1.9 super heat.
    Hi side 178 Psi, 3 subcool
    18 temp drop across the coil... 81 return - 63 supply.
    I couldn't figure out what's wrong with it

  2. #2
    you want to check the square feet of the house it's look like you compressor is a week your low side should be about 60 65 PSI
    make sure your square feet is the same as the regional NO extension added also I'm not sure where the system if it's an attic make sure you don't have any doubt leaks including the return
    http://www.liebertairconditioning.com

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
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    25,758
    Wet bulb temps would help.

    As would airflow.


    I do not suspect your compressor, but I do suspect multiple problems here.

    Low airflow and low charge most likely.

  4. #4
    Join Date
    Feb 2012
    Posts
    1,268
    Quote Originally Posted by DNMechanical View Post
    I'm working on a 3 ton Trane ac system....bout 12 yrs old...
    The house is not cooling properly.
    83 degree outdoor
    Low side 74 psi, 1.9 super heat.
    Hi side 178 Psi, 3 subcool
    18 temp drop across the coil... 81 return - 63 supply.
    I couldn't figure out what's wrong with it
    1.9 is a bit low for super heat.

    Does the unit have a TXV or fixed orifice?

    What type of refrigerant is in the unit?

    I'm thinking it's overcharged but we need more information on the unit.

  5. #5
    Join Date
    Mar 2012
    Location
    Grand Prairie, TX
    Posts
    27
    r-22. fix orifice. I pretty sure it had multiple problems but just couldn't figure it out ..unit is in attic.. no no air leak....

  6. #6
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,758
    Quote Originally Posted by AStudent

    1.9 is a bit low for super heat.

    Does the unit have a TXV or fixed orifice?

    What type of refrigerant is in the unit?

    I'm thinking it's overcharged but we need more information on the unit.
    Subcooling indicates a low charge.

    Low superheat tends to point towards a low airflow, particularly since the subcooling is low as well.


  7. #7
    Join Date
    Feb 2012
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    High side pressure too high...low side is spot on..with a fixed orifice. What does this indicate?

  8. #8
    Join Date
    Sep 2008
    Location
    Western PA
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    Quote Originally Posted by DNMechanical
    r-22. fix orifice. I pretty sure it had multiple problems but just couldn't figure it out ..unit is in attic.. no no air leak....
    Not thinking about an air leak, I'm thinking that you don't have enough air moving across the evaporator coil.

  9. #9
    Join Date
    Mar 2012
    Location
    Grand Prairie, TX
    Posts
    27
    if not enough air move across evap, it will cost low suction presure

  10. #10
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    Mar 2012
    Location
    Grand Prairie, TX
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    @ASTUDENT.... high side is too low (NOT HIGH). low side is about right...

  11. #11
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    Sep 2008
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    Western PA
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    Quote Originally Posted by AStudent
    High side pressure too high...low side is spot on..with a fixed orifice. What does this indicate?
    Pressures alone are largely meaningless.

  12. #12
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    Sep 2008
    Location
    Western PA
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    Quote Originally Posted by DNMechanical
    if not enough air move across evap, it will cost low suction presure
    It will cause low Superheat, first,

    Your 81 degree return temp would help to keep that suction pressure up.


    Did you measure the airflow?

  13. #13
    Join Date
    Sep 2008
    Location
    Western PA
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    Quote Originally Posted by DNMechanical
    @ASTUDENT.... high side is too low (NOT HIGH). low side is about right...
    Low high side pressure would be consistent with low load caused by low airflow.


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