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tx valve

A txv is adjustable so you can set it up to maintain a desired amount of superheat. Compressor manufacturers will tell you how much superheat is required at the compressor for optimimum performance and protection. It's fairly standard to see a 10-15 degree superheat, though some want as much as 35. Once the system is stable and your superheat is set where you want it, you shouldn't have to touch it again. Make sure your bulb placement is correct, secure, and well insulated. Unless someone has played around with it, the txv is basically set and forget. I'd apply some leak lock at the stem cap on that leaker-

Comments

  • curiousity kills
    curiousity kills Member Posts: 118
    tx valve

    Is it normal for refrigerant pressure to come out the bottom of a tx when you remove the cap to adjust superheat
  • Jim Pompetti
    Jim Pompetti Member Posts: 552


    Sometimes there is a set you can tighten at the point of ajustment,otherwise tighten cap to pervent leak lockleak may help
  • curiousity kills
    curiousity kills Member Posts: 118


    HUH?I went to lossen the cap to adjust superheat and pressure and dripping refridgerant came out.Iended up pulling into sucback adjusting evacuating then opened system,My question was is this normal?
  • Techman
    Techman Member Posts: 2,144
    TXV

    Hi! Was the TXV working properly, other than needing a slight adjustment?
  • will smith_4
    will smith_4 Member Posts: 259
    txv

    You should not expect a leak at a txv adjustment stem any more than you would expect a leak at any service valve. If the valve leaks and tightening the packing does not stop it, it has incurred damage (probably by being overheated when it was installed)-and should be replaced.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Definitely NOT Normal

    This is definitely NOT normal.

    One question, though. The TXV has a one-line job description, which is to maintain constant evaporator superheat. Prior to your attempting to adjust it, was the valve maintaining superheat? If so, why are we adjusting it?

    If the TXV is not maintaining superheat, adjusting the spring pressure is not going to correct a mechanical problem with the valve.

  • curiousity kills
    curiousity kills Member Posts: 118


    Actually the tx was union type and installed after brazing so it was not overheated.The valve was a Lennox and had a one to three ton rating.I was installing on a 2.5 ton. On first start up superheat was at 20 and I was trying to bring to 10.I was told to adjust because the tonnage flexablity of the valve.Please correct me if I am wrong.Thanks
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Just be VERY Careful

    When adjusting the TXV make certain that you turn the adjustment screw in SMALL increments at a time (0.5 to 1 turn), and be sure to allow the system to operate for at least 10 minutes between adjustments. Make certain that you repeat your superheat calculations before each adjustment.
  • Techman
    Techman Member Posts: 2,144
    Hay curiousity kills

    On any "start-up " the superheat is going to out of bounds for awhile,then once the system is stabilized an accurate superheat can be taken and adjusted.Enjoy!
  • curiousity kills
    curiousity kills Member Posts: 118


    Thanks for the responses but my original question was is it normal for pressure to come out when removing the cap
  • Techman
    Techman Member Posts: 2,144
    Just Courious

    As The professor said -NO- .but I'm still courious about the superheat adjustment!
  • curiousity kills
    curiousity kills Member Posts: 118


    well then why is it there if you dont touch it
  • will smith_4
    will smith_4 Member Posts: 259
    if you get pressure when removing the cap

    There is a leak in the valve-replace it.
  • Techman
    Techman Member Posts: 2,144
    Courious

    It's there to be touched,BUT,BUT,BUT,from what to what?
  • steve_29
    steve_29 Member Posts: 185


    It's not surprising to find that the valve leaks... some more than others.

    Make sure the nut is tightened so the leak is contained at the stem and not escaping.

    Curiosity does kill... and in HVACR it's usually the compressor.

    good luck

  • curiousity kills
    curiousity kills Member Posts: 118
    thanks for the response

    > A txv is adjustable so you can set it up to

    > maintain a desired amount of superheat.

    > Compressor manufacturers will tell you how much

    > superheat is required at the compressor for

    > optimimum performance and protection. It's fairly

    > standard to see a 10-15 degree superheat, though

    > some want as much as 35. Once the system is

    > stable and your superheat is set where you want

    > it, you shouldn't have to touch it again. Make

    > sure your bulb placement is correct, secure, and

    > well insulated. Unless someone has played around

    > with it, the txv is basically set and forget. I'd

    > apply some leak lock at the stem cap on that

    > leaker-



  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    So....

    So txv manufacurers can sell a lot more valves when people adjust them when they shouldn't. The saddest part of the whole thing is that if a technicians does not know how to properly adjust a TXV they an successfully kill the compressor.

    Just remember..... Small adjustments.... wait 15 minutes.... make superheat calculations...

    No race..... take it slow.... nice and slow....
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