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  1. #1
    Join Date
    May 2019
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    Lightbulb TXV Sensing Bulb

    Hey guys,
    I have recently installed a new TXV on Nordyne evaporator coil. Model number: B4VM-X30K-B
    Serial Number: 920773D. The issue I am having is when I have it in cool mode, my Suction pressure goes up to 125psi and drops down to 80, then it just keeps doing the same thing over and over. It takes about a minute for the pressure go up then back down. I have a feeling its my sensing bulb just not placed properly. Does anyone have any ideas as to what it could be? If it is the sensing bulb, some advice on placement and insulation to use over it. The system runs on R-410a. Any help would be really appreciated.
    Thanks

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Quote Originally Posted by Matador429 View Post
    Hey guys,
    I have recently installed a new TXV on Nordyne evaporator coil. Model number: B4VM-X30K-B
    Serial Number: 920773D. The issue I am having is when I have it in cool mode, my Suction pressure goes up to 125psi and drops down to 80, then it just keeps doing the same thing over and over. It takes about a minute for the pressure go up then back down. I have a feeling its my sensing bulb just not placed properly. Does anyone have any ideas as to what it could be? If it is the sensing bulb, some advice on placement and insulation to use over it. The system runs on R-410a. Any help would be really appreciated.
    Thanks
    What are the SH & SC readings?

  3. #3
    Join Date
    May 2019
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    2
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    Thread Starter
    I only checked the SH, but it kept fluctuating going from 50 and dropping to 20. Im a new tech, still learning.

  4. #4
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    6,543
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    Please have your post moved from AOP to the tech to tech forum.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  5. #5
    Join Date
    Oct 2011
    Location
    Gladstone, Oregon (Portland)
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    Sensing bulb. Depends how you installed everything too.

  6. #6
    Join Date
    Dec 2012
    Location
    columbus, OH
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    Whats it do when you remove it from the suction line?


    Sent from my iPhone using Tapatalk

  7. #7
    Join Date
    Dec 2009
    Location
    maroon lazyboy
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    2,581
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    Quote Originally Posted by Matador429 View Post
    I only checked the SH, but it kept fluctuating going from 50 and dropping to 20. Im a new tech, still learning.
    Hello Matador and welcome...
    You say you are still learning, and that is good. All good technicians are still learning.

    What you are describing sounds as if the system is low on charge and the txv is not getting enough liquid... rather a slug of liquid every now and then. Txv systems need to be charged by sub-cooling.
    Keep asking questions it is how you learn. Good luck.

  8. #8
    Join Date
    Dec 2015
    Location
    Ohio
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    A quick check of subcooling will tell a lot. This number is essential to know when charging a system with a TEV.

  9. #9
    Join Date
    Jul 2009
    Location
    Columbia, MD
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    Quote Originally Posted by frankhvac View Post
    A quick check of subcooling will tell a lot. This number is essential to know when charging a system with a TEV.
    Could be low on gas
    Could be incorrect bulb placement. (If in vertical position, cap tubes should be coming off the top of bulb, not the bottom)
    Possible you overheated it
    Could be a piece of brazing rod slag stuck in the equalizer line.


    Sent from my iPhone using Tapatalk

  10. #10
    Join Date
    Apr 2006
    Location
    Tyler, Tx
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    Bulb should be place either between 2 and 5 o'clock position or the 7 and 10 o'clock position. NEVER on top or on bottom of pipe. It needs to be insulated. Once you do this verify subcooling. ~8-10 SC, depends on system. Report back what you did...
    Philippians 4:13
    I can do all things in him that strengthen me.
    Apostle Paul inspired by GOD.

  11. #11
    Join Date
    Dec 2007
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    Quote Originally Posted by Artietech View Post
    Bulb should be place either between 2 and 5 o'clock position or the 7 and 10 o'clock position. NEVER on top or on bottom of pipe. It needs to be insulated. Once you do this verify subcooling. ~8-10 SC, depends on system. Report back what you did...
    Which most mfrs DON'T do, insulate or position.
    The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
    Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
    from an excerpt by Paul Jacob in Sun City, AZ

  12. #12
    Join Date
    Apr 2006
    Location
    Tyler, Tx
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    Quote Originally Posted by pacnw View Post
    Which most mfrs DON'T do, insulate or position.
    That is correct, but as I pull the bulb off the line to braze, it does not bother me. I think Trane is the only one who ships it installed, which means some installers are overheating the bulb because they do not bother with pulling the panels off, let alone wrapping the bulb with a rag...
    Philippians 4:13
    I can do all things in him that strengthen me.
    Apostle Paul inspired by GOD.

  13. #13
    Join Date
    Jan 2019
    Location
    Vero Beach, Florida
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    295
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    Quote Originally Posted by Artietech View Post
    That is correct, but as I pull the bulb off the line to braze, it does not bother me. I think Trane is the only one who ships it installed, which means some installers are overheating the bulb because they do not bother with pulling the panels off, let alone wrapping the bulb with a rag...
    Lennox does as well. I cant tell you how many horizontal installs Ive seen where the bulb is still in the vertical position.

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