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  1. #1
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    won`t bring box below 53 deg

    suction 34#
    Head 185# 4 deg drop across coil 53-49
    evap coil 46 deg
    suct line @ evap 50 deg
    liq line @ evap 72 deg

    Russell cond RC11/2H12 mod
    89F10374 ser

    Russell evap AE36-140
    010521

    is this unit overcharged

    R-12 system box 12x8x7

    any suggestion???????

    [Edited by dandyme on 06-15-2004 at 11:54 PM]
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  2. #2
    Join Date
    Apr 2004
    Posts
    161
    R12
    34psi = 36deg
    185psi= 132deg

    How did you get evap coil 46deg, thermometer inserted into coil?

    Let me know if Im wrong.

    Evap superheat is 50deg minus 36deg, 16deg evap superheat.

    Condensing temp is approx 132deg minus 72deg liq line temp, total subcooling 60deg.

    Air in 53deg minus 36deg boiling point, 17deg temp difference.

    4 deg drop across evap coil.

    My first impression is metering device is starving evap. Head pressure is a bit high also but it might be dirty or high ambient. I would suggest looking at expansion valve adjustment/replacement and checking/cleaning condensor coil both.

  3. #3
    Join Date
    Jun 2004
    Posts
    160
    checking/cleaning condensor coil both.

    I agree with ucp, clean the coils then check your system

  4. #4
    change the compressor. 34# suction will not get you close to temp.

  5. #5
    Originally posted by ucp
    R12
    34psi = 36deg
    185psi= 132deg


    My first impression is metering device is starving evap. Head pressure is a bit high also but it might be dirty or high ambient. I would suggest looking at expansion valve adjustment/replacement and checking/cleaning condensor coil both.
    If TXV was starving coil suction would be low not high. If you want to maintain regular cooler temps with R-12 you need at least an 18# suction. Check the chart.

  6. #6
    P.S. another random thought. High discharge might be another indicator of bad compressor not dirty condenser. Broken disch valves will reduce refirerant flow thus high suction, but cause an awful lost of heat to be passes to the high side due to disch gas entering and leaving cylinder with broken valves. Lots of heat generated but no refrigerant flow. Thus the high subcooling. Focus on the compressor.

  7. #7
    read this post. same problem almost


    http://hvac-talk.com/vbb/showthread.php?threadid=53788

  8. #8
    Join Date
    Apr 2004
    Posts
    161
    [i]
    If TXV was starving coil suction would be low not high. If you want to maintain regular cooler temps with R-12 you need at least an 18# suction. Check the chart. [/B]
    Your right, I think we all are trying to get him there.

  9. #9
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,478
    The higher head pressure could also indicate there's a blend of some sort in there and the hack that put it there didn't mark the unit.

    I'd still guess bad valves. Close off the suction and see how low it'll pump down. If it won't go to at least 10" Hg, replace the pump.

  10. #10
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    Thanks....

    ucp-yes, 1st thing after I walk in, jab temp probe in coil.
    Evap & Cond coils already clean.
    pumped down last night.........didn`t bypass lp cutout....shutdown at 5#

    It`s better to be silent and thought the fool; than speak and remove all doubt.

  11. #11
    Join Date
    Apr 2004
    Posts
    161
    dandyme:

    I curious what you found out and how you repaired this. I sure would like to know so I can store that info up in the brainbox.

  12. #12
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    Issue not resolved yet.
    Compressor pulls down to 20" vac.
    Haven`t spent much time on this box, we can`t seem to get there until midafternoon--------that bites, guy comes in at 8:00 every morning.
    This unit also has an intermittent high head trip out.
    I was really hoping the condenser would not pump down.
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  13. #13
    Join Date
    May 2004
    Posts
    12,261
    Dan...

    Is this a new customer? Have you or your guys worked on the box before? Are you sure you have R12? Could you have non-condensables in the line or a mix of refrigerant? It acts like it has 22 in it with a 12 power element.

    What size TXP? and is it an R12 head? With a blend like R414B (Hotshot) your superheat says you are starving the coil. How is the sight glass? Full or bubble?

    [Edited by lusker on 06-17-2004 at 11:04 PM]

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