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  1. #14
    Join Date
    Dec 2002
    SouthEast NC ICW & Piedmont Foothills
    Been doing this restaurant for several years.
    All records show to be R-12, never changed over-we don`t know why.
    Sight glass clear.
    Contamination has crossed our minds.
    Owner wants issue resolved before his vacation 07-04-04.
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  2. #15
    Join Date
    May 2004

    Just hate to say this but,

    1. One of your guys may have mixed the refrigerant by mistake. Or..

    2. If it was ever low on refrigerant and there was a blend in the system you have to determine if fractionation has occurred. (Loss of component blend)

    3. If a zeotropic blend was used, a full sight glass indicated an overcharged system. 80% charge when replacing 12. You need to see those bubbles.

    If you see your TXP hunting you can rule out the valve being bad but not its adjustment. If you can't get the evaporator suction line temperature below 50 degrees then take this 10 minute step before evacuating and virgin charge.

    Take a suction line temp at the evap coil. Run the TXP in (counting the turns) two turns. After a few minutes recheck the temp on the suction line. You need to get that suction line temp down a good 20 degrees, 50 is way too high. If the temp goes up, reverse the TXP 4 turns out and recheck suction line temp. If no change, recover and virgin fill and mark the system with refrigerant type for the next guy.

    The above posts are good and directing you to the correct area. With that system clean and the compressor good, 50 degree suction line at the evaporator, fan blades turning the correct rotation then this issue can be corrected. It has to be one of three things or a combination of.

    1. Overcharged, remember you said the hi pressure limit was kicking from time to time

    2. TXP out of adjustment or bad

    3. Refrigerant mixed or fractionated

  3. #16


    Wow, talk about over doing the simple. If you think the gas charge is wrong or contaminated pump the system down and let it set. measure the ambient temp and compare to the refrigerant pressure. Check your temp pressure chart to see if the pressure matches what it should be for R-12. This should take all of about 15-30 minutes tops, including a small break for restroom and coffee if required. If the system looks like it is still R-12, focus on the compressor. It is not doing its job. TX valve is not starving the coil!!! If it was the pressure would be lower than it is. Starved coil does not cause increase in suction pressure. You need at least 18# suction for R-12 to make a med temp cooler.

    To quote the great Scotty from Stat Trek....
    "I can not change the Laws Of Physics Captain"

  4. #17
    Join Date
    Apr 2004
    #18 psi suction if box was 40deg or so. Its 53deg air in to evap, so normally you would expect 30-35 deg evap temp w/r12? Looks more and more like its not r12 in there.

  5. #18
    That is easy to eleiminate or prove. Pump it down and do a pressure temp check.

  6. #19
    Join Date
    Apr 2004
    Originally posted by refer dude 2479
    That is easy to eleiminate or prove. Pump it down and do a pressure temp check.
    Looks like thats the way to go. Perhaps dandyme could just shut down condensing unit and wait for 20 minutes and tell us the box temp and his suction press/temp.

  7. #20
    close the liquid line service valve. Pump it down and do the temp pressure check on the high side verses the ambient at the condenser.

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