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Thread: EXV Hunting

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    EXV Hunting



    Dear all,

    I am using electronic expansion valve on my 15 kW scroll machine and it was running perfectly fine. Recently there was a small leak and i corrected it. After topping up some gas to counter the leak, my system was never stable and the super heat hunts between 3 to 6 deg K compared to earlier fluctuation which is less than 1 K.
    Some one advice me that i should entirely evacuate the system and the recharge it to original charge level.

    Even after that, my superheat still hunts. What could be the problem?

    In between, i also would like to know more on the electronic expansion valve, mainly on the operating principles of the valve. I have found some info on the internet but not much technical explanations. Any sort of information is very much appreciated. I am using Emerson EX 2 together with the accompanied controller

    Please help.

    Regards,
    jaya



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    Re: EXV Hunting

    Last edited by Brian_UK; 30-08-2009 at 11:42 PM. Reason: Spelling
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    Re: EXV Hunting

    Check that during previous work on system you did not move/damaged/disconnected/etc.. sensors of valve controller.
    Also check parameters on valve controller.
    BTW what is valve controller model # ?
    Also, what is your subcooling?
    Last edited by nike123; 30-08-2009 at 10:52 AM.

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    Re: EXV Hunting

    I have reset the controller to the factory setting and then set them according to my specifications. I have also check the mounting of the sensor and other wirings. they all look ok to me.

    About the controller i am using Emerson EC2-391 with EX2 valve.

    My subcooling has been the same all the while approximately 1K

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    Re: EXV Hunting

    Quote Originally Posted by jayaeros View Post
    I have reset the controller to the factory setting and then set them according to my specifications. I have also check the mounting of the sensor and other wirings. they all look ok to me.

    About the controller i am using Emerson EC2-391 with EX2 valve.

    My subcooling has been the same all the while approximately 1K
    That subcooling is low!

    If we presume some errors in reading of instruments, it could be easy that you don't have 100% liquid at EXV entrance. That lead to bad superheat control.
    I would add charge until 4-5K subcooling and then look how EXV behave.
    But before, you should check condenser air/water flow and if it is clean (delta T). Same goes for evaporator!

    Where did you measured subcooling? Is it affected by air from condenser? Do you have liquid receiver? What kind of system is that?
    Last edited by nike123; 01-09-2009 at 11:43 AM.

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