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Thread: Just line temp.

  1. #1
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    Just line temp.

    I was wondering can we find out the psi in a line just by the temp of that line?

    I have a sealed system (freezer - reachin - turboair) I measured the line temp:
    lowside - 51.5' and highside - 151.9'
    P-T chart R134a reads (lowside - 49psi and highside - 263psi)
    P-T chart R404a reads (lowside - 109psi and highside - 453psi)

    My freezer stats R404a but it can't be? I called the manufacture and they stated that it is correct.
    Would you please inlighten me on this.. please....... BTW the freezer is working fine.
    This thread is not to ask for repaire just to get educated.

  2. #2
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    I guess what he said make sense, refrigerant in a tank at room temperature is different then a refrigerant being pushed around by a compressor. P-T chart is only referring to refrigerant that is not being pushed around by the compressor...

  3. #3
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    If there is a liquid/vapor mixture you definitely can use a pt chart, though a compressor definitely influences the pressure and temperature of the refrigerant in the system with the dynamic forces upon the gas.


    Suppose you have an r404a jug and you just finished charging every drop of liquid from the jug into a small compressor pack, now the jug is only vapor. With all vapor there will be superheat present, and that will throw away the usefulness of a pt chart (pt relationship won't exist with pure vapor)

  4. #4
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    Would that apply to all liquid justlike all gas?

  5. #5
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    Quote Originally Posted by the_4rs View Post
    Would that apply to all liquid justlike all gas?
    all liquid? that would be hard to answer, liquid does subcool at 100% quality while staying at the same pressure (for example, like the liquid line of a home ac unit or mechanical subcooler of supermarket). If you have to know the pressure and temperature of a refrigerant at a given location in the system, you absolutely need a thermometer of a pipe-clamp type and a refrigerant pressure gauge, and using superheat and subcooling calculations (basic math), you'll know exactly what's going on in your system.


    You could have 50 psig on the low side of an ac system with 15 degrees evaporator superheat (considered ideal), or 50 psig and 0 degrees evaporator superheat (could be dangerous for compressor)

  6. #6
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    without knowing the PSI, can we use the temperature splits from the evap and the condensor to get a good enough idea of the charge in a sealed system? Split at evap 15.4' and the split at condensor 11.3' also the box temp is 13.3'....

  7. #7
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    I see... Thank you...

  8. #8
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    I think sub cool and super heat would add a few isues https://www.youtube.com/watch?v=DGYL...e_gdata_player

    Sent from my SPH-L720 using Tapatalk

  9. #9
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    Quote Originally Posted by TACKERDOWN View Post
    I think sub cool and super heat would add a few isues https://www.youtube.com/watch?v=DGYL...e_gdata_player

    Sent from my SPH-L720 using Tapatalk
    This is the best video I've seen about superheat/subcool

  10. #10
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    Thank you

  11. #11
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    Quote Originally Posted by TACKERDOWN View Post
    I think sub cool and super heat would add a few isues https://www.youtube.com/watch?v=DGYL...e_gdata_player

    Sent from my SPH-L720 using Tapatalk
    Excellent video. Thanks.

    RIP Mr. Gizmo End of watch 10/27/2016
    It was a good situation, until everything went wrong!
    Rub some dirt on it and walk it off...
    We will always know it should have worked!
    “There’s a clear cause and effect here that is as neat and predictable as a law of physics: as government expands, liberty contracts.” Ronald Reagan

  12. #12
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    I was going to try and explain but im more of a hands on type. Glad to help.

    Sent from my SPH-L720 using Tapatalk

  13. #13
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    Quote Originally Posted by the_4rs View Post
    without knowing the PSI, can we use the temperature splits from the evap and the condensor to get a good enough idea of the charge in a sealed system? Split at evap 15.4' and the split at condensor 11.3' also the box temp is 13.3'....
    What is every ones ideal splits on Evap and Condensor?

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