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  1. #1

    Question Automatic Expansion Valves

    How do they work, what's the purpose of the adjusting screw, is it a good or bad valve, what's the position of the vale when in the off cycle?

  2. #2
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    I won't go into a great deal of detail as you are a new member and I don't konw your qualifications.

    Basically, an Expansion Valve is a type of metering device that maintains a constant superheat as per the manufacturers specifications. There is a sensing bulb on it that connects to the powerhead and the powerhead in turn opens and closes a diaphram to regulate and maintain the superheat.

    Adjustable Expansion valves are used typically in commercial applications and allows the technicain on site to adjust the superheat to acheive the manufacturers specifications.

    There are advantages and disadvantages to the adjustable. Biggest advantage is the expansion valve can be used on any brand system for its rated size. And since most manufacturers have their own superheat specs., it can easily be adjusted to reflect that. Biggest disadvantage is if the technician does not know its an adjustabe of if the technician is not familiar with how to adjust them, problems could be encountered.

  3. #3
    Join Date
    Apr 2004
    Posts
    136
    In refrigeration the term "automatic expansion valve" normally refers to a valve used to maintain a constant outlet pressure such as an evaporator pressure requlator. The stem in this case would be the pressure setting.

  4. #4

    Thank You

    Thank you iraqveteran. I am a student as of right now and I needed some additional info for one of my classes.

  5. #5
    Join Date
    Dec 2003
    Location
    Half way between North pole and Equator
    Posts
    947
    An "AXV" controls outlet pressure only. It does not care what the superheat is. The superheat on a AXV system is dependant on the load on evap coil.

    A "TXV" attempts to control superheat of evap coil by sensing suction line temp on outlet of Evap coil. As superheat increases, valve will be opened to allow more refrig into coil.

    An AXV valve has no sensing bulb, but a TXV does.

  6. #6
    Join Date
    Jan 2005
    Location
    steeler nation
    Posts
    2,025
    IV IV IX

    use your head for something other than a hat rack.......Gerry

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