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Thread: pump down / txv

  1. #1
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    pump down / txv



    working on a split system. Lennox S- series 5 ton outdoor condenser. CBX27UH air handler
    410a. Diagnosed last week as a bad TXV as the suction pressure was dropping constantly as the head pressure stayed constant.
    Adding refrigerant did nothing. There is a high heat load in the space - 90 deg F return temp.
    The air handler is about 15 - 20 feet below the condensing unit which is on the roof. There is a p-trap installed on the suction line
    We replaced the TXV today. No change. I told the tech to remove the bulb and put it outside the unit. The suction stabilizes however, it is too low at 115 psi.
    Head Pressure is 250 psi (which is also low). One thing that the tech noticed, is that after we had pressure tested, and vacuumed the lines and then were ready to release our charge into the lineset and evap - he opened the suction side valve and no refrigerant came out. This is a scroll compressor. Is this normal?

    Regards,

    JBW



  2. #2
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    Re: pump down / txv

    Could there be a kink in the line set?
    Mostly found in Oxfordshire, UK :)

  3. #3
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    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
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    Re: pump down / txv

    Although scrolls have a check valve on the discharge Copeland do state there is a large amount of refrigerant will re-expand back into the low pressure side of the compressor at the end of a pump down cycle.
    Last edited by Brian_UK; 17-05-2013 at 09:53 PM.
    Brian - Newton Abbot, Devon, UK
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