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Thread: What is TXV

  1. #1
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    What is TXV

    I think the Comfort-R feature on my Trane furnance requires an a/c coil with TXV. Does anyone know what TXV is and why it would be critical for use with Comfort-R? I have an 11 seer, 6 year old Lennox a-coil and don't know if it has TXV.

  2. #2
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    Thermal eXpansion Valve

    The TXV modulates to allow the precise amount refrigerant to flow thru the evap coil to maintain ideal coil temp. It modulates from the heat or lack of heat sensed by the sensing bulb on the suction line leaving the evap.

    The TXV is sized to the coil & condenser and usually mandates the requirement of a hard start kit to assist the compressor in starting.

  3. #3
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    A txv is nothing more than a metering device for your refrigerant which adjusts the flow of freon into your coil to maintain a certain superheat. It cares about nothing except the superheat, which is there to protect your compressor, and to make your system a little more efficient in fluctuating conditions. If on the outside of your airhandler/coil, you see a large nut on the smaller copper line,or two nuts(compression fittings), you probably have a piston. Post model numbers and one of these Guru's can tell you....
    If everything was always done "by the book"....the book would never change.

  4. #4
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    Quote Originally Posted by smokin68 View Post
    A txv is nothing more than a metering device for your refrigerant which adjusts the flow of freon into your coil to maintain a certain superheat. It cares about nothing except the superheat, which is there to protect your compressor, and to make your system a little more efficient in fluctuating conditions. If on the outside of your airhandler/coil, you see a large nut on the smaller copper line,or two nuts(compression fittings), you probably have a piston. Post model numbers and one of these Guru's can tell you....
    i watched your boys go down Christmas Day..........TO is an a$$,and not a very good football player anymore...........hang in there brother...it will get better,this coming from a true Skins fan and yes,you should have a txv metered coil

  5. #5
    Thermal eXpansion Valve
    It actually stands for *Thermostatic* eXpansion Valve. It's one of the most common types of expansion valves (other common types are capillary tube and CPEV) in use today. It can adapt to load changes, making it work better than capillary tubes for variable loads. The easiest way to see if it has a TXV is to look for a sensing bulb on the suction line. Or follow the liquid line to the evaporator coils and see if there's one installed. If all you see is a barrel (filter drier) and some thin tubes, it's capillary tube. If you see a strange looking valve with 3 or 4 pipes going to it (1 very thin (sensing bulb line), 2 fairly thick (coil and liquid line), 1 somewhat thin (equalizer if present)), it's a TXV. A CPEV will look like a TXV but without a sensing bulb or equalizer line.

  6. #6
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    Quote Originally Posted by star882 View Post
    It actually stands for *Thermostatic* eXpansion Valve. It's one of the most common types of expansion valves (other common types are capillary tube and CPEV) in use today. It can adapt to load changes, making it work better than capillary tubes for variable loads. The easiest way to see if it has a TXV is to look for a sensing bulb on the suction line. Or follow the liquid line to the evaporator coils and see if there's one installed. If all you see is a barrel (filter drier) and some thin tubes, it's capillary tube. If you see a strange looking valve with 3 or 4 pipes going to it (1 very thin (sensing bulb line), 2 fairly thick (coil and liquid line), 1 somewhat thin (equalizer if present)), it's a TXV. A CPEV will look like a TXV but without a sensing bulb or equalizer line.
    and just to add to this,the sensing bulb is filled with freon independent of the systems charge.....this is how the freon is throttled/metered through the txv itself

  7. #7
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    Quote Originally Posted by star882 View Post
    It actually stands for *Thermostatic* eXpansion Valve. It's one of the most common types of expansion valves (other common types are capillary tube and CPEV) in use today. It can adapt to load changes, making it work better than capillary tubes for variable loads. The easiest way to see if it has a TXV is to look for a sensing bulb on the suction line. Or follow the liquid line to the evaporator coils and see if there's one installed. If all you see is a barrel (filter drier) and some thin tubes, it's capillary tube. If you see a strange looking valve with 3 or 4 pipes going to it (1 very thin (sensing bulb line), 2 fairly thick (coil and liquid line), 1 somewhat thin (equalizer if present)), it's a TXV. A CPEV will look like a TXV but without a sensing bulb or equalizer line.
    Yes - my typo, too many things going on at one time.

  8. #8
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    Thanks everyone for the great information. The model is a Lennox C23-51-1, an 11 seer, 4 ton A-coil. It's about 6 years old. Can anyone tell me if this model has TXV? Also, any thoughts on why the confort-r feature would require it? Here's the thread I found that mentions it needs it http://www.hvac-talk.com/vbb/showthr...ight=comfort-r

    I will also try and post a picture of my coil.

  9. #9
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    Dec 2006
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    Here are some pic's from when they were installing my Trane furnace and had the A-coil exposed. Not sure if you can tell from these if it has TXV or not. Name:  DSCF2902.jpg
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    Thanks again for everyone's help

  10. #10
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    Don't look to be a TEV, I sure don't like having a drier that close to the metering device, I have had a lot of pistons wash out because of folks putting the drier that close, maybe it don't make any difference but I have always had bad experiences with the driers that close.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  11. #11
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    Cool Ive never liked it either

    Quote Originally Posted by mrbillpro View Post
    Don't look to be a TEV, I sure don't like having a drier that close to the metering device, I have had a lot of pistons wash out because of folks putting the drier that close, maybe it don't make any difference but I have always had bad experiences with the driers that close.

    ...but actually read directions on a drier box that said to install the drier close to the expansion device

  12. #12
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    Well it has lasted 6 years without any issues, so hopefully I won't have any problems. Also, it doesn't look like I can do much about it now.

    Thanks for the heads-up.

  13. #13
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    Quote Originally Posted by air2spare View Post
    ...but actually read directions on a drier box that said to install the drier close to the expansion device

    Yes but that's not an expansion device, probably a piston device.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

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