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  1. #1
    Join Date
    Jul 2011
    Location
    SLO/central coast,CA
    Posts
    128

    what is superheat ?

    R-134a with spring pressure 9.5 psig =5.5* and evap 30.5 psig =35*
    how to calculate the superheat?

  2. #2
    Join Date
    Mar 2005
    Location
    N.J.
    Posts
    149
    WHAT??????????????

  3. #3
    Join Date
    Apr 2007
    Location
    Saint Augustine, Florida, United States
    Posts
    1,156
    call a tech. save yourself some money.

  4. #4
    Join Date
    Jul 2005
    Posts
    5,576
    Quote Originally Posted by cfe View Post
    R-134a with spring pressure 9.5 psig =5.5* and evap 30.5 psig =35*
    how to calculate the superheat?
    Bulb pressure equals spring pressure plus evap outlet pressure, so
    P_bulb = 9.5 + 30.5 = 40psig

    SH is the bulb saturated temp minus the evap saturated temp (assuming that bulb temp is equal to suction line temp)

    From the P/T chart
    SH=45-35=10

  5. #5
    Join Date
    Jul 2011
    Location
    SLO/central coast,CA
    Posts
    128

    Smile

    Quote Originally Posted by hvacrmedic View Post
    Bulb pressure equals spring pressure plus evap outlet pressure, so
    P_bulb = 9.5 + 30.5 = 40psig

    SH is the bulb saturated temp minus the evap saturated temp (assuming that bulb temp is equal to suction line temp)

    From the P/T chart
    SH=45-35=10
    thanks hvacmedic.
    i thought there is no way to figure out SH with the info provided or just when evap in equilibrium only and maybe cross bulb charge will have different SH reading.

    i did the same calculation but end up with 5 SH. i misread 30.5psig to 35.5 psig=40*. 40psig=45*

    i always rely on thermometer and gauge to get SH ans SC reading.

  6. #6
    Join Date
    Jul 2005
    Posts
    5,576
    Quote Originally Posted by cfe View Post
    thanks hvacmedic.
    i thought there is no way to figure out SH with the info provided or just when evap in equilibrium only.
    i did the same calculation but end up with 5 SH. i misread 30.5psig to 35.5 psig=40*. 40psig=45*

    i always rely on thermometer and gauge to get SH ans SC reading.
    Yes, that was assuming stable operation, and an ideal TXV. Of course no such TXV exists, so this was all correct only on paper.

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