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Thread: TEV problem

  1. #1
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    877
    Working on a HP system.
    It was making ice in the evap.
    84 deg ambient
    a real low suction pressure, a normal for ambient discharge pressure.
    19 degree SH.
    Checked the TEV, the bulb was hanging in the air.
    Restrapped it to the suction line ( screw tightend mount was still attached to suction line inside the evap case).
    Melted ice
    Suction and discharge pressures the same as before, now with 30 deg superheat?????????????
    Attempted to adjust TEV, found turned almost all the way clockwise (perhaps 1/16 of a cw turn remaining)

    Couldn't get any change to SH.
    Has the TEV bulb lost charge or did a previous tech screw things up?

    I think either way time the change the TEV, lucky it's a flare fitting.

    Any other ideas?

    I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.
    ― Benjamin Franklin

  2. #2
    Post all the needed data for a competent answer to your question.

    Model number __ HP
    Metering device TXV

    SP __ /T __ LP __ /T __
    ST __ LT __
    SH __ SC __
    AT 84 CT __
    IWB __ IDB __
    Evap ST __ LT __
    Comp A __ Rated A __

    Would be nice to see the data before and after...

    Mounting the TXV bulb did change the SH, so what makes you think its not functioning? Could be that the last tech didn't have the time or experience to fix the issue, and left the bulb hang to open the valve fully (to lower SH).

  3. #3
    Join Date
    Jul 2005
    Posts
    88
    Did you re insulate the bulb?

  4. #4
    Join Date
    Mar 2005
    Location
    South/West of Quebec in the other part of Canada
    Posts
    2,331
    check inlet sceen on the TEV

  5. #5
    igwt777 is offline Professional Member - T&B bad email address
    Join Date
    Jul 2005
    Posts
    172
    Need all the basic info.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    I don't think I'm awake yet.

    Did you turn the stem cw, or ccw.

    cw would increase sh, ccw would decrease sh.
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  7. #7
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    877
    I'd melted the ice off after strapping the TEV.
    My assumption was that an ice block doesn't have much heat to give off. The clean evap was picking up enough heat to evap any ref and heat to 30 deg SH. I use a pipe clamp probe to take line temps.

    Austin TX, hot summer humid day, ambient for the ODU was in the shade with a slight breeze.
    Model number __ HP Goodman CPLE60-1
    Metering device TXV

    SP 58 /T 24 LP 245 /T 115
    ST 41 LT __ Didn't record, so can't figure subcool.
    SH 19 SC __
    AT 84 CT __
    IWB __ IDB __,
    Evap ST __ LT __
    Comp A __ Rated A __

    15 degree split from supply register to return register.
    The home has 2 ac systems, the one for the sleeping areas was working.

    Looking at the numbers again, the 245 pressure is only valid if a high efficiency system.
    Looked up on the net, 10 SEER system. Indicates system is low on charge at LP 245. Argh. Still paying tuition in wasted time. It's a 3 hour round trip.

    Any other thoughts or suggestions?




    I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.
    ― Benjamin Franklin

  8. #8
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    877
    I'd melted the ice off after strapping the TEV.
    My assumption was that an ice block doesn't have much heat to give off. The clean evap was picking up enough heat to evap any ref and heat to 30 deg SH. I use a pipe clamp probe to take line temps.

    Austin TX, hot summer humid day, ambient for the ODU was in the shade with a slight breeze.
    Model number __ HP Goodman CPLE60-1
    Metering device TXV

    SP 58 /T 24 LP 245 /T 115
    ST 41 LT __ Didn't record, so can't figure subcool.
    SH 19 SC __
    AT 84 CT __
    IWB __ IDB __,
    Evap ST __ LT __
    Comp A __ Rated A __

    15 degree split from supply register to return register.
    The home has 2 ac systems, the one for the sleeping areas was working.

    Looking at the numbers again, the 245 pressure is only valid if a high efficiency system.
    Looked up on the net, 10 SEER system. Indicates system is low on charge at LP 245. Argh. Still paying tuition in wasted time. It's a 3 hour round trip.

    Any other thoughts or suggestions?


    I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.
    ― Benjamin Franklin

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    R22 at 58 psi has a sat temp of 32, you posted 24?

    Which way did you turn the txv stem?

    If its cranked in all the way, you'll get a high sh no matter what.
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  10. #10
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,346
    If the TXV stem is all the way in, you'll run a high superheat, as increasing the valve's spring pressure will increase the closing force on the valve. Remember, the only opening force on a TXV is the thermostatic bulb pressure.

    Here's what I'd do if I found an adjustable TXV where the stem had been turned since the factory (after doing as you have by securing the bulb and correcting any other problems); turn stem all the way in until it seats. Then turn it counterclockwise, counting each full rotation of the stem, until it backseats (is fully out counterclockwise). Next take number of turns counted and divide it in half, then turn stem in that number of rotations. Start system, let it balance out, and check superheat at evap using suitable probe and digital thermometer. Adjust as necessary to get correct superheat.

    This, of course, assumes the thermostatic bulb, charge, and powerhead still respond correctly to changes in evaporator superheat, and that any other external factors such as dirty coils, airflow issues, clogged inlet strainer to TXV, etc, have been corrected.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,095
    Good advise shop.
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    How many times must one fix something before it is fixed?

  12. #12
    Originally posted by allan38
    Looking at the numbers again, the 245 pressure is only valid if a high efficiency system.
    Looked up on the net, 10 SEER system. Indicates system is low on charge at LP 245. Argh.

    Any other thoughts or suggestions?
    Loose this thinking... what link did you get this from?

  13. #13
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    877
    Installed a new Danfoss TXV, the 4.5 ton orifice was a number 6, the old one had a number 3 (5.2KW or about 2 1/2 ton). The undersized orifice in the TXV was causing the problem. It's evidently been that way since installed in 02. I think the installing tech mistook 5.2KW for 5 ton.
    Followed box diagrams on setting up the TXV. (Left turn to stop, then right 2x360. Clever instructions, all in drawings and numbers. No words in any language.

    I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.
    ― Benjamin Franklin

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