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  1. #1
    Join Date
    Jul 2010
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    53

    no superheat, no subcooling

    Here is the situation... Design pressures are 150/300psi with 12 degree subcooling...

    Actual conditions are 92Psi liquid at a temperature of 69F. High pressure side is at around 220Psi and about 12F BELOW saturation temperature. Cooling isn't really doing much indoors and runs constantly.

    Is the compressor on the way out or is there a charge issue here. Forgive me as I am fairly new to the service industry.

    Thanks in advance guys

  2. #2
    Join Date
    May 2009
    Posts
    257
    you have 14 deg superheat on r22 at that pressure and temp. The 92 is the suction not the liquid. The liquid (or high pressure or head pressure) temp should read below the saturation temp (it does SUBCOOL the refrigerant after all).

    Your suction pressure is kinda high. This could be caused by hot temperature inside or high airflow. Is this a txv system?

  3. #3
    Join Date
    Jul 2010
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    53
    R22 is the refrigerant

  4. #4
    Join Date
    Aug 2006
    Location
    Columbus Ohio
    Posts
    1,977
    Quote Originally Posted by 02powerstroke View Post
    Here is the situation... Design pressures are 150/300psi with 12 degree subcooling...

    Actual conditions are 92Psi liquid at a temperature of 69F. High pressure side is at around 220Psi and about 12F BELOW saturation temperature. Cooling isn't really doing much indoors and runs constantly.

    Is the compressor on the way out or is there a charge issue here. Forgive me as I am fairly new to the service industry.

    Thanks in advance guys
    I am kind of lost in your post...

    Fill this out for me:

    Refrigerant type (22,410,134)?
    Type of system (split, package, chiller)?
    Metering device (TXV, orifice, cap tube)?
    Suction pressure?
    Suction line temp?
    Liquid line pressure?
    Liquid line temp?
    Return air temp?
    Temp drop across the evap coil?

    This will help us get started.
    UA LU189

    10mm, because it's better than .45acp

  5. #5
    Join Date
    Jul 2010
    Posts
    53
    I'll get to a laptop quick and fill that out..

  6. #6
    Join Date
    May 2009
    Posts
    257
    What is your coil temp difference? Do you have duct leakage to have high suction like that?

  7. #7
    Join Date
    Jul 2010
    Posts
    53
    Quote Originally Posted by zw17 View Post
    I am kind of lost in your post...

    Fill this out for me:

    Refrigerant type (22,410,134)? R22
    Type of system (split, package, chiller)? Split
    Metering device (TXV, orifice, cap tube)? TXV
    Suction pressure? 92 psi
    Suction line temp? 69F
    Liquid line pressure? ~220 psi
    Liquid line temp? 108F
    Return air temp? Didn't measure this, however the thermostat is set to 79F.
    Temp drop across the evap coil? Supply air temperature is 67F.
    This will help us get started.
    I edited the quote to include the requested information

    Also, if my suction line pressure is 92psi and my saturation temp is about 57F. If my suction line temperature is 69F, doesn't that mean I have no subcooling?

  8. #8
    Join Date
    Dec 2010
    Location
    Down by the river
    Posts
    1,579
    Quote Originally Posted by 02powerstroke View Post
    I edited the quote to include the requested information

    Also, if my suction line pressure is 92psi and my saturation temp is about 57F. If my suction line temperature is 69F, doesn't that mean I have no subcooling?
    no that means you have 12* superheat. Line temp - Sat temp = superheat for suction and subcool for liquid.

    I really reccomend you learn what this is, the superheat / subcool as you can not diagnose a refrigeration issue w/o this. It's kinda like your blood pressure
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  9. #9
    Join Date
    Aug 2006
    Location
    Columbus Ohio
    Posts
    1,977
    You have 14*F superheat
    You have 0*F subcooling

    That 0*F subcooling tells me you are way undercharged.
    UA LU189

    10mm, because it's better than .45acp

  10. #10
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    1,041
    Quote Originally Posted by 02powerstroke View Post
    if my suction line pressure is 92psi and my saturation temp is about 57F. If my suction line temperature is 69F, doesn't that mean I have no subcooling?
    The suction line is superheated gas returning to the comp from the indoor coil. If sat. temp is 57 and the gas is 69, you have 12F of superheat.

  11. #11
    Join Date
    May 2004
    Location
    Frederick, MD
    Posts
    880

    Something

    is not adding up here. How can you have 12-14 degree superheat and no subcooling? The TXV will be wide open with no liquid to it, only vapor. S/H should be much higher.

  12. #12
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    1,041

    Smile

    Quote Originally Posted by gregp View Post
    is not adding up here. How can you have 12-14 degree superheat and no subcooling? The TXV will be wide open with no liquid to it, only vapor. S/H should be much higher.
    Saturated refrigerant can be any combination of liquid and vapor, as long as both are present.

  13. #13
    Join Date
    Aug 2006
    Location
    Columbus Ohio
    Posts
    1,977
    02, have you tried adding gas? I would start by adding until you see you liquid line temp start to drop a bit. No more than 2-3lbs though.

    If you don't have the manufactures recommendation on target subcooling I would shoot for 10*F to start. Check your temp drop and superheat and report back to us.
    UA LU189

    10mm, because it's better than .45acp

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