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  1. #1
    Join Date
    Jun 2011
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    Question High discharge pressure, high suction pressure. with high super heat and subcooling

    Hi, I just put a new compressor on a gas pack. I charged it to the correct amount of refrigerant o the name tag. My ambient temp. is 100 degrees and the unit running with a high high side pressure a high suction pressure and high superheat and sub cooling. The indoor temp is 87 degrees. i was told that the high indoor temp is why my pressures and temps. are high. And need to wait until the area can be cooled to around 80 degrees to get better pressures. Is that true? or what else could be wrong?

  2. #2
    Join Date
    Jul 2003
    Location
    Massachusetts
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    288
    what are the actual pressures?

  3. #3
    Join Date
    Jun 2005
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    171
    What are the actual pressures? Actual superheat and subcooling temperature and room temperature?
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  4. #4
    Join Date
    Jul 2007
    Location
    The Hot South
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    1,310
    Quote Originally Posted by Drew26 View Post
    Hi, I just put a new compressor on a gas pack. I charged it to the correct amount of refrigerant o the name tag. My ambient temp. is 100 degrees and the unit running with a high high side pressure a high suction pressure and high superheat and sub cooling. The indoor temp is 87 degrees. i was told that the high indoor temp is why my pressures and temps. are high. And need to wait until the area can be cooled to around 80 degrees to get better pressures. Is that true? or what else could be wrong?
    It would nice if you posted the temps and pressures. Does it have a TXV? Your pressures and temps will be high when the indoor and ambient temps are high.

  5. #5
    Join Date
    Jun 2011
    Posts
    11

    Question

    I have 325psi on the high side and 87psi on the low side. The superheat is 31 degrees and the sub cooling is 40 degrees. It does not have a txv.

  6. #6
    Join Date
    Jul 2003
    Location
    Massachusetts
    Posts
    288
    did you run a vac on this system before charging?

  7. #7
    Join Date
    Jun 2010
    Location
    U.A. (upper Alabama)
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    854
    I would check it again after it pulled the space down.

  8. #8
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
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    4,277
    Quote Originally Posted by Drew26 View Post
    I have 325psi on the high side and 87psi on the low side. The superheat is 31 degrees and the sub cooling is 40 degrees. It does not have a txv.
    A SC reading of 40 degrees would put your line temp at 97 degrees, which would be cooler than your outdoor ambient.

    The only way for that to happen would be from incorrect instrument readings or non-condensibles in your system. Evacuate,pump it down and re-charge to name plate then adjuste your charge when it starts cooling down.
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  9. #9
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,067
    Did you use a micron gauge?

  10. #10
    Join Date
    Feb 2010
    Location
    In a boiler room
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    How did you figure the subcooling? Do you still use: suction pressure - suction line temp?

  11. #11
    Join Date
    Jul 2007
    Location
    The Hot South
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    1,310
    Quote Originally Posted by chuckcrj View Post
    How did you figure the subcooling? Do you still use: suction pressure - suction line temp?
    Subcooling is liquid pressure converted to saturated condensing temp - liquid line temp.

  12. #12
    Join Date
    Jul 2007
    Location
    The Hot South
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    1,310
    Quote Originally Posted by ACFIXR View Post
    A SC reading of 40 degrees would put your line temp at 97 degrees, which would be cooler than your outdoor ambient.

    The only way for that to happen would be from incorrect instrument readings or non-condensibles in your system. Evacuate,pump it down and re-charge to name plate then adjuste your charge when it starts cooling down.
    Good catch!

  13. #13
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,067
    Quote Originally Posted by R123 View Post
    Subcooling is liquid pressure converted to saturated condensing temp - liquid line temp.
    That is true, in a thread in June the OP thought you calculated it by the method in my post. Just wanted to make sure he was measuring right.

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