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  1. #27
    Join Date
    Jun 2004
    Location
    Location:Raleigh NC
    Posts
    9,637
    Quote Originally Posted by beachtech View Post
    if split system get more accuracy by pump down and just running OD fan
    Good point
    If you help others then you are a Success

  2. #28
    Join Date
    Jul 2005
    Posts
    5,574
    Quote Originally Posted by beachtech View Post
    if split system get more accuracy by pump down and just running OD fan
    How do you measure the pressure in the condenser when it's pumped down? Yesterday I checked for noncondensables by running the condenser fan, but I didn't pump the system down. (High subcooling high superheat, TXV coil.) I got a perfect match between ambient and SDT, so no noncondensables. Determined it was a restriction, like I first suspected. Then to track down the restriction I dropped subcooling at the liquid line service valve to 1 deg by reducing system charge and bypassing LP switch, then measured liquid line temp drop from the service valve to the TXV inlet. 5 deg total drop. This means that the liquid line, including the filter dryer, was using up only 6 degrees of subcooling. Not the problem. Determined that it has a bad TXV (no inlet screen). TXV to be replaced Monday.

  3. #29
    Join Date
    Mar 2005
    Location
    5,000 ft
    Posts
    2,207
    Quote Originally Posted by beachtech View Post
    if split system get more accuracy by pump down and just running OD fan
    When valves are closed for pump down the service ports are open to line set and not the condenser... Am I missing something else?

  4. #30
    Join Date
    Jan 2008
    Posts
    63
    good tip thanks

  5. #31
    Join Date
    Oct 2007
    Location
    ATLANTA
    Posts
    120
    Quote Originally Posted by hvacrmedic View Post
    How do you measure the pressure in the condenser when it's pumped down? Yesterday I checked for noncondensables by running the condenser fan, but I didn't pump the system down. (High subcooling high superheat, TXV coil.) I got a perfect match between ambient and SDT, so no noncondensables. Determined it was a restriction, like I first suspected. Then to track down the restriction I dropped subcooling at the liquid line service valve to 1 deg by reducing system charge and bypassing LP switch, then measured liquid line temp drop from the service valve to the TXV inlet. 5 deg total drop. This means that the liquid line, including the filter dryer, was using up only 6 degrees of subcooling. Not the problem. Determined that it has a bad TXV (no inlet screen). TXV to be replaced Monday.

    Hi

    Just curious do you guys typically find moisture in the system as showing a higher or lower pressure than what the proper temp and pressure relationship is supposed to be.

    Also is there a trend that certain noncondensables tend to follow which helps to identify them?

    Thanks

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