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  1. #1
    Join Date
    Sep 2002
    Posts
    12,195

    Why does this line sweat ?

    Situation -

    Walkin box - about 30' by 60' by 12'

    Two evaps - hung at about 10' on one long wall.

    Two condensing units outside at ground level.

    The line sets are vertical and external to the walkin box.

    Suction line is insulated - liquid line is not insulated.

    One unit is running - the other unit is not running. The 'off' system is pumped down and has an isolation ball valve closed at the condensing unit.

    95 day. The suction line sweats from the closed ball suction up towards the evaporator.

    Why is that? What is happening to produce refrigerating effect in a dead-ended suction line?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  2. #2
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,259
    You basically have the isolated suction line acting as a heat pipe.

    Refrigerant vapor is condensing in the evaporator and draining down the suction line, where the condensed liquid picks up heat and boils off, to be condensed again in the evaporator.

    It sounds like it's not really pumped down, as there is enough refrigerant to start this heat pipe action in the evap.

  3. #3
    Join Date
    Jun 2004
    Posts
    847
    Where is the liquid line solonoid?
    Is it short cycling?

  4. #4
    Join Date
    Sep 2002
    Posts
    12,195

    Well; I am looking for clues <g>

    This has been a long-term problem-child system. Losing compressors at a 10-1 ratio to the identical system next to it. Every kind of failure: seized, broken, no-pump, burnout, shorted. Pattern-less and apparently random failures. At start-up all conditions are textbook. Daily re-checks show the same consistent conditions of operation. Then a short while later the compressor fails.

    I guess I will replace the liquid-line service valve - top of the receiver - and the LLSV this time around. As, so far as I can see; they both must leak through.

    PHM
    ------




    Quote Originally Posted by icemeister View Post
    You basically have the isolated suction line acting as a heat pipe.

    Refrigerant vapor is condensing in the evaporator and draining down the suction line, where the condensed liquid picks up heat and boils off, to be condensed again in the evaporator.

    It sounds like it's not really pumped down, as there is enough refrigerant to start this heat pipe action in the evap.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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