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  1. #1
    Join Date
    May 2012
    Location
    NC
    Posts
    56

    TXV bulb install question

    Several weeks ago I followed the failed maintenance supers's(several guys) attempts to fix a no cool. I found contaminated R-22 and a TXV installed with the piston still installed. The bulb was also not secured to the piping, nor was it touching anything, just sitting in the air stream. I removed the TXV, pulled a good vacuum and charged the system with new R-22, problem fixed.

    Returned to the same property last week, different apartment. This system showed low on Freon, I don't remember the exact numbers but the SH was high and the Subcool was low. It also had a TXV, also not secured to anything just floating around the air stream. I didn't pump down and check for a piston. The pressures did change however when I held the bulb in my hand. I added Freon and left the Subcool at 10. They haven't called back saying it isn't working, but it's created a question in my mind.

    These are old Suntherm units, Heat pump. A coil, the bulb jammed between the cover panel and the U bends at the edge of the coil, so not really out in the middle of the air stream.

    The question is; Does a TXV bulb always have to be in contact with the piping? What will happen if it isn't? I did notice that when I added R-22, High side would shoot up very quickly, then slowly fall and stabilize.

  2. #2
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    The bulb must be attached to the outlet of evaporator and insulated. It response to the amount of super .most are installed at the 10 or 2 o'clock position

  3. #3
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    ive always thought i heard 5 and 7 o clock

  4. #4
    Join Date
    Jul 2012
    Location
    Richland, WA
    Posts
    248
    When I was in school they said anywhere from 6 to 9 o clock or 3 to 6 o clock


    Sent from my iPhone using Tapatalk

  5. #5
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    No oil from refrigerant settles On bottom.Vapor rises therefore 3 ,9,2,or5 gives u best reading.

  6. #6
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    I'm sorry 3,9,2,10 o'clock position

  7. #7
    Join Date
    Jul 2012
    Location
    Richland, WA
    Posts
    248
    Quote Originally Posted by hewitt View Post
    I'm sorry 3,9,2,10 o'clock position
    mmm, cause the powerpoints that I got from when in school say different
    Name:  TXV.jpg
Views: 418
Size:  30.9 KB

  8. #8
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    Some books say as long as it's mounted horizontal

  9. #9
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    This is becoming interesting.Going to move a bulb around and check some numbers

  10. #10
    Join Date
    Jul 2012
    Location
    Richland, WA
    Posts
    248
    Quote Originally Posted by hewitt View Post
    Some books say as long as it's mounted horizontal
    Refrigeration Training Services/NATE training slides say Must sense true suction temperature
    - not bottom of pipe
    - not top of pipe

  11. #11
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    So what position does nate say is the correct placement

  12. #12
    Join Date
    Jul 2012
    Location
    Richland, WA
    Posts
    248
    Quote Originally Posted by hewitt View Post
    So what position does nate say is the correct placement
    from there power points 3 and 9 o clock are the best areas

    Name:  TXV 2.jpg
Views: 224
Size:  47.0 KB
    Last edited by caheiman30; 08-13-2012 at 01:46 AM. Reason: added picture

  13. #13
    Join Date
    Jan 2012
    Location
    WEST COLUMBIA S.C.
    Posts
    293
    Service valves where u hook up gauges are 3 or9 if u look at them.If these ports were located on top would the boiling are saturation temp be the same on gauges or would it make that much difference

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