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Thread: adjusting txv's

  1. #1
    Join Date
    Dec 2008
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    55

    adjusting txv's

    i came across this a few times already in my 2 year career, today on a walk-in fridge top half of evap is iced up, txv iced up at distributor, good airflow, clean evap, fans run, checked pressures after de-icing, 35/205 r-22, full sight glass. didn't suspect charge issues with a full sight glass. high superheat at evap 30 degress. opened up the txv a few turns got the superheat to 12 degrees. everything seemed to run well after that

    my question is, why would the txv need to be adjusted all of a sudden?, this walk-in has always ran well for the two years i've been servicing this restaurant, have never had isssues, is the txv getting restricted and i'm compinsating by opening it up some more? or is it slowly crapping out, or is that normal to need to adjust txv's at times ?

  2. #2
    Join Date
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    Your power head could be week or your pins sticking.
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  3. #3
    Join Date
    Jun 2001
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    Michigan
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    did you check the liquid inlet screen to the TXV.

  4. #4
    Join Date
    Nov 2005
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    386
    was the box temp within 10* when checking that superheat reading?

  5. #5
    Join Date
    Dec 2008
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    55
    yes, box temp was 45 degrees when i checked original superheat

  6. #6
    Join Date
    Aug 2008
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    92
    There are several possible reasons. But likely the power head has lost a very small amount of its charge, so then the spring pressure to power head pressure was out of whack, and you put in back in line when adjusted. Or a previous tech adjusted it when it wasn't the problem, and this was truly a call back.

  7. #7
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    So swinginutters have you been back? give us a up date.
    I love the smell of phosgene first thing in the morning:

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  8. #8
    Join Date
    Mar 2008
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    Canada
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    its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.

  9. #9
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    Quote Originally Posted by balzano View Post
    its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.
    there is an electronic txv now i havent seen that yet?

  10. #10
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    Quote Originally Posted by neumonic View Post
    there is an electronic txv now i havent seen that yet?
    yes, there is and has been one for a lil while now
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  11. #11
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    Quote Originally Posted by balzano View Post
    its mechanical, so its normal to be adjusted each few months, with the new electronic txv we will not have this problem, superheat adjusted= good refrigeration cycle= life time compressor.
    and we would glady use your money to purchase this new electronic valve

    and, lmao

    we have blamed pushrods, inlet screen, and powerhead loss of charge... what about installation? is the thing installed properly?

    is the sensing bulb in the right location? what o'clock position is it on the suction line? is it on a vertical line? is it mounted in an oil trap?

    i don't understand why someone would think a txv needs to be constantly adjusted

    the only thing a TXV does, is adjust and maintain SH. right?
    If Guns Kill People, Do Pencils Misspell Words?

    http://www.youtube.com/watch?v=An2a1...eature=related

    Before we work on artificial intelligence why don't we do something about natural stupidity?

  12. #12
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    Quote Originally Posted by neumonic View Post
    there is an electronic txv now i havent seen that yet?
    You've got your stepper valves that sense system SH with pressure transducer and temp sensor to compute superheat and drive the valve open or closed incrementally.
    You've got your liquid injection valves that open on increase in superheat to squirt liquid through an orifice. They're an on / off type valve. They can be controlled the same as the stepper or with an inlet an an outlet temp sensor to work out the SH. Have you ever walked into a supermarket refrigerated section and heard a clicking from the cases? That's the injectors opening.
    Then there's the old thermal type valve that has a variable resister in the suction line that feeds current to a heater in the top of the valve where yout TX valve power element sits. If I recall correctly, the heater heats a bimetallic disk that flexes in and out to drive pins as in a normal TX valve. It's the simplest of the 3 as it needs no electronics.
    Mistakes are a part of being human. Appreciate your mistakes for what they are: precious life lessons that can only be learned the hard way. Unless it's a fatal mistake, which, at least, others can learn from. Al Franken, "Oh, the Things I Know", 2002

  13. #13
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    Quote Originally Posted by beachtech View Post
    yes, there is and has been one for a lil while now
    i have only been in the trade a very short 2 years so i havent seen much yet thats why i was interested....ive seen the eeprs , just not any electronic txv
    How do they operate?

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