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  1. #27
    Join Date
    Sep 2008
    Western PA
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    On suction lines 7/8” OD and larger, the
    surface temperature may vary slightly
    around the circumference of the line. On
    these lines, it is generally recommended that
    the bulb be installed at 4 or 8 o’clock on the
    side of the horizontal line, and parallel with
    respect to the direction of flow. On smaller
    lines the bulb may be mounted at any point
    around the circumference, however locating
    the bulb on the bottom of the line is not
    recommended as an oil-refrigerant mixture
    is generally present at that point.
    The above from Sporlan 10-11.

    Field experience says that the 'clock' position doesn't matter a whole lot. A good insulation wrap means more than quibbling over 2 o'clock vs 3 o'clock and gets you to beer o'clock a whole lot faster.

  2. #28
    Join Date
    Nov 2011
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    With some applications, mounting the sensing bulb outside is the only option. Here's a link covering the vertical issue.

  3. #29
    Join Date
    Nov 2008
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    Of course the bulb has to been in contact with the piping.
    Depends upon what the bulb is sensing if loose and not contacted properly will possibility flood the evaporator among other sporatic conditions.

  4. #30
    Join Date
    Jan 2015
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    Yes the bulb must contact the line. For best performance any place but 12 and 6.

    Insulation is a must if you want it to be accurate.

    As for mounting vertical or horizontal or the location of the fill nipple it depends. But almost every application I've seen requires horizontal positioning. Some industrial / commercial TXV designs are faster acting than the normal comfort cooling applications and correct orientation can be an issue. Some have a dip tube inside the bulb and orientation keeps the cap tube opening in the gas space in the bulb. It has been my experience if the fill nipple is up, the dip tube in the bulb is up and in the gas space, not in any liquid that may be in the bulb . Next time you install one take a hard look at the bulb. I've seen some that say UP. I know some old Dunham Bush (Big 4) chillers that have the sensing bulb strapped to a short section of return tubing that is on a 45 degree angle (from the factory) and upside down. A DB factory guy told me that provided the fastest response time to load changes

  5. #31
    Join Date
    Nov 2006
    Southeastern Pa
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    .....another thread rises from the dead!!!!

    Unless you have something truly new to add to an old thread, the better idea is to start a new thread of your own.

    Adding something truly new is rare.....
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

    AOP Forum Rules:

  6. #32
    Join Date
    Feb 2004
    New Mexico
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    I do Timebuilder. I once ran into a (I won't say tech) that seemed to want to solve performance problems by unclamping the bulb and letting it dangle in the air stream. He had done this to a couple of RT units that were actually suffering from plugged evaps.
    Another said he always charged to a 225# head regardless.
    This business is like the wild west.
    I should have played the g'tar on the MTV. MK

    You can be anything you want......As long as you don't suck at it.

    USAF 98 Bomb Wing 1960-66 SMW Lu49

  7. #33
    Join Date
    Jul 2012
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    I make sure to open the txv until the suction line is beer can cold on a hot day. Works for me. I don't worry about no subheat or supercoolin.

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