Results 1 to 5 of 5
  1. #1
    Join Date
    Feb 2012

    EXV forced closure?

    I recently noticed that my air handler / indoor coil has a pair
    of dry-contact input terminals to force its EXV to CLOSED during
    cooling mode.

    When/why would you want to do this, and/or why would such a
    function want to be able to be externally automated? I can't
    imagine how it could be good for the rest of the system.



  2. #2
    Join Date
    Aug 2003
    Fort Worth, TX
    What indicates that this is what the set of dry contacts are for? Dry contacts are often for alarm triggering purposes.
    • 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.

  3. #3
    Join Date
    Mar 2009
    Hobbit it this on your Daikin system we have talked about before?

  4. #4
    Join Date
    Feb 2012
    Yup, the Daikin FTQ type air handler. Quoting from the
    install manual description for option block terminals 9,10:
    "Receives input: Forced closure of indoor unit Electronic
    Expansion Valve during cooling operation. (dry contact)"

    Seems like a strange thing to want an input for. Note: this
    isn't the same as "forced off" that you'd use for safety
    switches, condensate-pump overflows, etc.


  5. #5
    Join Date
    Sep 2012
    Central Florida
    Sorries did not notice this was in the ask a pro section.
    Last edited by Elfshadow; 09-10-2012 at 03:42 PM. Reason: was in wrong section.

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