York Heat Pump Expert out there ?
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  1. #1
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    I have worked with the Yorks for quite some years, and know them well, but I am baffled by something.

    On the Yorkmate demand defrost controller, there are 3 temp sensors, an Ambient, a Discharge and the Liquid Line. The Ambient and Discharge are clear. The Liquid Line sensor is the question. I well understand that it reads the freon temp exiting the condenser coil and compares it to the ambient to determine if there is good heat transfer to the ambient air. My problem is that they call it the "Liquid Line" sensor, when there is normally not liquid in that line. True there may be some condensing in the coil under some temperature conditions, but it is not truly a "liquid" line.

    Any ideas why this term was used ?

    paul

  2. #2
    Join Date
    Oct 2004
    Posts
    3,400
    The liquid line is always the liquid line, and always high side.

    Liquid flows in the opposite direction during reverse cycle, but it's still liquid.

  3. #3
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    To clairify, the "Liquid Line" sensor is not on the traditional liquid line, as you would think. It is located on the line from the condenser coil that goes to the reversing valve. This point of the circuit is hot gas from the compressor in A/C mode, and cool gas to the suction accumulator in heating mode (in both cases through the reversing valve). It is the same basic location of a defrost termination switch in a conventional time-temp defrost control.

    Since where the sensor is mounted is not a 'iquid line, I just wonder why they call it a liquid line sensor.

    paul

  4. #4
    Join Date
    Oct 2004
    Posts
    3,400
    I guess that's why you wanted a York expert. (I'm not one.)

    That IS confusing.

    That part of the system NEVER sees liquid.

  5. #5
    Join Date
    Sep 2000
    Location
    Granite City IL USA
    Posts
    765
    What you are describing is the discharge sensor.

  6. #6
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    Lorne:

    No, the discharge sensor is right on the compressor discharge line. This is the "other" sensor that is called the "Liquid Line".

    paul

  7. #7
    the refrigerant should be all liquid when leaving the condenser that is why it is a liquid line sensor, the liquid line is the line that leaves the condenser and it is the liquid line when it leaves the evaporator in the heat mode.

  8. #8
    Join Date
    Oct 2002
    Posts
    369
    Originally posted by airworx
    the refrigerant should be all liquid when leaving the condenser that is why it is a liquid line sensor, the liquid line is the line that leaves the condenser and it is the liquid line when it leaves the evaporator in the heat mode.



    Exactly...well said.
    Havin'a good time is what life is all about.

  9. #9
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    I would agree, a bit. When heating, the expanding refrigerant in the evaporator (outside condenser coil) picks up heat from the ambient, and some will condense to a liquid, but it can't be much. If it were it would flood the compressor, since the freon goes to the suction of the compressor. True that the suction accumulator is there to help separate the gas from the liquid, but if it were fully liquid, it could be a problem for the compressor.

    Would it be better to call it "a bit of liquid line" ?

    I understand what is happening, but I still think calling it a "liquid line" sensor is misleading.

    paul

  10. #10
    Join Date
    Sep 2000
    Location
    Granite City IL USA
    Posts
    765
    This is what tecmen described:

    To clairify, the "Liquid Line" sensor is not on the traditional liquid line, as you would think. It is located on the line from the condenser coil that goes to the reversing valve.

    Liquid line does not go to the reversing valve.

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