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Thread: TXV

  1. #1
    Join Date
    Apr 2005
    Location
    illinois
    Posts
    257
    I just had a new coil placed with a factory installed txv. I was wondering what signs a homeowner might notice if the txv was not functioning properly. I saw on another post that when brazing the lines in, that the sensing bulb should be protected. I do not know if the sensing bulb was near the brazed joint but the installer did not put a wet rag or shield between the txv and his torch.
    The new coil is a Amer Std TXCO65S3HPCO. The condensor is Allegiance 12 2A7A2048A1000AA. Is the sensing bulb or any other component that is heat sensitive near where the lines are brazed?

  2. #2
    most residential techs dont wrap rags around anything.
    if txv had a problem you would run low suction and high superheat, also the service valves outside that the installer didnt wrap up will start leaking soon or already is.

  3. #3
    Join Date
    Apr 2004
    Posts
    7,680
    The HO would see a lack of performance, he then calls a tech who can then properly troubleshoot the system.



  4. #4
    Join Date
    Apr 2005
    Location
    illinois
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    257
    I do appreciate the replies but I was hoping for more specifics. Specifically what would a homeowner look for that might indicate a problem with a TXV. I requested the TXV because of what I have learned on this site. I was also able to realize that I didn't receive a coil that had a TXV because of this site. This site has been great.
    I would like to be confident that I am receiving the benefits of a TXV now that I have one but given what I said in the original post I am concerned that the sensing bulb or other component coud have been heat damaged and may fail to perform as designed. Would poor performance mean high bills or poor dehumidification since the coil might not be cold? Is there a way I can have a tech check the function of the TXV? What would he test? I am trying to educate myself since the posters on this site seem to really know how to do things the right way. The information I have obtained on this site has more than a few times enabled me to avoid acting on a poor suggestion
    by a contractor. Thanks.

  5. #5
    Join Date
    Apr 2004
    Posts
    7,680
    I really dont know what answer you're looking for. If the TXV has failed, the unit will no longer cool. When the unit no longer cools, it's time to call for service. Then the service technician, with his training can evaluate the system and find the reason for it not cooling. There is no special failure mode that would indicate to a homeowner that the TXV has failed.

    Yes, there are tests he can perform to verify the TXV's operation but long before he gets to that point he needs to establish that the TXV is getting a solid column of refrigerant, verify the bulb is properly attached, rule out any other restrictions etc.

    TXV bulbs should be protected from extreme temperatures when brazing. Mainly because the pressure on the top of the valve could bottom out in the diaphram and bend or warm the metal diaphram. Inside the TXV are metals made of steel and brass. Heating can expand the pieces and force them to seize. Any tecnician worth a salt, will take steps to prevent this and certainly not connect the bulb until the lines have cooled.

  6. #6
    Join Date
    Aug 2005
    Location
    Sarasota Florida!! hot & humid
    Posts
    926
    Post all the vitals if it shows ok now it will hopefully stay that way.

  7. #7
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,001
    Originally posted by heetseeker
    I do appreciate the replies but I was hoping for more specifics. Specifically what would a homeowner look for that might indicate a problem with a TXV. I requested the TXV because of what I have learned on this site. I was also able to realize that I didn't receive a coil that had a TXV because of this site. This site has been great.
    I would like to be confident that I am receiving the benefits of a TXV now that I have one but given what I said in the original post I am concerned that the sensing bulb or other component coud have been heat damaged and may fail to perform as designed. Would poor performance mean high bills or poor dehumidification since the coil might not be cold? Is there a way I can have a tech check the function of the TXV? What would he test? I am trying to educate myself since the posters on this site seem to really know how to do things the right way. The information I have obtained on this site has more than a few times enabled me to avoid acting on a poor suggestion
    by a contractor. Thanks.
    Sometimes it's true a person can get to much info. "especially here" the TXV is ok I can assure you if not it would not cool, so just let it be you got to have many more concerns with just everyday life that should be higher on the agenda.
    __________________________________________________ _______________________
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  8. #8
    Join Date
    Apr 2005
    Location
    illinois
    Posts
    257
    I appreciate the replies. What are the symptoms of low suction or high superheat? I saw in another post that an improperly functioning TXV will hunt, overfeed or starve a system. Do these cause any symptoms? It seems like you are telling me that as long as I have cooling the TXV is working properly. Is that correct?

  9. #9
    pull the bulb off of the suction line, if suction pressure goes up and superheat down (suction line gets colder) the the valve is working. also check the subcooling of the condenser (normally marked on the nomenclature ) to the actual subcooling. mormally will be 9 to 12 degrees, but could be higher depanding on the efficiency of the system. i have seen design subcooling at 18 degrees.

  10. #10
    Join Date
    Apr 2005
    Location
    illinois
    Posts
    257
    Thanks airworx but your explanation is too technical for me. are there symptoms that a homeowner, not a HVAC tech, could check for?

  11. #11
    Join Date
    Nov 2005
    Location
    BAKERSFIELD CA.
    Posts
    78
    if you dont under stand cuz its to technical try this put a thermo meter in the supply duct (the one that blows ) take the temp and then put a thermo metyer in the return ( the one that suxxxx)take the temp then subtract the big number from the small and if you have an 18 to 22 degree diff in temp call it good 74
    -54
    ----
    20
    or we could go into sub cooling

  12. #12
    Join Date
    Apr 2004
    Location
    Bartlett, IL
    Posts
    6,619
    Wow, two hundred sumptin posts and you're still on this TXV thingamajigger....sounds like you're a bit too paranoid.

  13. #13
    Join Date
    Apr 2005
    Location
    illinois
    Posts
    257
    Again thanks for the replies. Big game, I will try to check the temperature drop this summer. 2Hot, I am cautious because of all the problems posters have described on this forum. Maybe we are just hearing about the problem systems, but many Pros have commented that less than ideal practices are common on installations.

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