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Thread: txv

  1. #1
    Join Date
    Feb 2005
    Could someone help me explain the difference between none-bleeding expansion valve and bleeding expansion valve and how are they connected differently?


  2. #2
    A none bleed expansion valve is a valve that will close completely, not to allowing the systems pressures to equalize. This helps prevent flooding the evaporator on the off cycle.

    A bleeding expansion valve does allow pressure equalization on the off cycle, were evaporator flooding is not a problem, and allows for a lower torque compressor for starting.

    Both valves would be connected the same. Only the internal parts are differant.

    These designs are for differant system applications. Changing valves on a system could cause the compressor to slug liquid, or a compressor starting problem.

    Why do you ask?

  3. #3
    Join Date
    Feb 2005

    I often got asked and don't know

  4. #4
    Some non bleed applicatins will use the TXV as a solenoid because it will provide 100% shut off and in place of using a large solenoid, You can use a small one on the externally equalizer line to act as a pilot duty solenoid and slam the valve shut.

  5. #5
    Join Date
    Aug 2003
    Fort Worth, TX
    A non-bleed valve will do as the others say; i.e. not allow system equalization to prevent floodback to the compressor upon system startup.

    It is also thought that a system that does not equalize after shutdown will spend less time coming back into its nominal operating parameters after it restarts. IOW the compressor isn't spending a lot of time pulling the evap back down to design saturated vapor temp/pressure since the pressure in the evap at startup is more or less already there.

    Non-bleed TXV's will require a start cap and potential relay on a single phase compressor.
    Building Physics Rule #1: Hot flows to cold.

    Building Physics Rule #2:
    Higher air pressure moves toward lower air pressure

    Building Physics Rule #3:
    Higher moisture concentration moves toward lower moisture concentration.

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