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  1. #1
    Join Date
    Aug 2003

    R410a TXV vs R22 TXV

    Recently I replaced many indoor coil which came with R410a TXV manf. installed. Keeping the condensing R22 unit, we must change the TXV compatible with R22.
    My question is what happens to the performance if we leave R410a TXV untouched.
    A- Evaporator coil gets flooded, because of....
    B- Evaporator coil starves, because of...
    C- This is funny, and all niebourhood will start laughing and make fun of you.
    Please be prompt ,explanatory and prove what you saying.
    PS. P1+P2=P3
    I'm learning

  2. #2
    Join Date
    Dec 2010
    Palm Beach,Fl.
    I would say that the TXV would flood the evap based on a lack of closing pressure from the suction line. Purely speculation of course but I know that if the situation was reversed, a 22 txv will starve the evap and the opening force from the bulb is the similar between the two.

  3. #3
    Join Date
    Jul 2009
    Columbia, MD
    i know if u have a r-410a system with an r-22 expansion valve at indoor coil you will starve the evaporator of refrigerant and have high superheat.

  4. #4

    Factory Feedback

    Got this from an engineer at Trane:

    I believe the problem is in the bulb charge. The charge used in a 410A valve bulb runs higher pressure because it is opposed by the pressure of the Equalizer port running at 410A pressures. The port sizes are usually not much different if at all. In the case of our Sporlan valves the port sizes are the same between 410A and R22.

    Scenario 1: 410A valve on an R22 system

    The bulb charge is higher pressure than the Eq port pressure. This will keep the valve open flooding the evaporator. If the valve has a smaller port, it may act as damage control here however the designed superheat will not be achieved regardless. It will likely either flood or hunt badly.

    Scenario 2: R22 valve on a 410A system.

    The bulb charge is lower pressure than the Eq port pressure. This will close the valve starving the evaporator. If the valve has a larger port, the larger port may help to compensate here however the superheat will likely run high.

  5. #5
    Join Date
    Jul 2012
    i would say if the suction line gets beer can cold its good. might have to add a lot of "freon" to it.

  6. #6
    Join Date
    Aug 2003
    Thanks to djsmalltx,
    You explained it scientificly.
    Please let me know if you want to add more detail or formula.
    How about the spring tension. they shouldent be the same!
    I'm learning

  7. #7
    Join Date
    Jun 2003
    Chicago, IL
    I recently fixed a lobster tank that had a 12 valve on a 404 system. This is the same scenario, a high pressure gas on a low pressure valve, the symptoms were a severely starving evaporator. I replaced the thermal element, (not even the whole valve) and it worked perfectly

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