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  1. #1
    Join Date
    Nov 2012
    Location
    Upstate NY
    Posts
    16

    Tracer VAS Setup Problem

    I have an IntelliPak RTU with cooling only, coupled with VariTrane VAVs (Comm3/Comm4), that are defined in Tracer Summit as a VAS. The system behaves properly in all respects but one.

    When in Unoccupied mode (controlled by schedule), after a few hours with RTU and all VAVs in "unoccupied" mode:
    1. The VAV units go into Night Heat/Cool mode to heat (all 8 of them, within a 1 hr. period, once it'sw cold enough)
    2. The VAV units open their air valves & heating coils to heat
    3. The VAS's AHU Fan Request = 'ON'
    4. The RTU's Present Value = Night Heat/Cool
    5. The RTU's Active Mode = Unoccupied Cooling (the RTU is cooling only)
    6. RTU Fan will not run.

    Not sure what I've missed, but any help would be grreatly appreciated.

  2. #2
    Join Date
    Jul 2007
    Location
    Mount Airy, MD
    Posts
    7,281
    Thread relocated to "Controls"

  3. #3
    Join Date
    Apr 2005
    Location
    Boulder,CO.
    Posts
    559
    Try a simple CPL program that will tell the RTU to go to Opt Start this will control the fan on keep OA Damper closed. ie:
    PROGRAM NIGHT_HEAT_COOL

    DEFINT Night_Heat_Cool

    DEFOBJ RTU, VAS

    /// This program controls the Present Value of an I-PAK to OPT/START

    /// If the Present Value of the vas is night heat cool

    ///Routine Execution: This program is executed every minute.

    ///Routine Text File:night_heat_cool.CPL

    RTU = {Retreat Bldg RTU}
    VAS = {Retreat VAS}
    IF (VAS.{Present Value} = 8)
    THEN
    CONTROL ({Retreat Bldg RTU}, {Present Value}, 1, 5, SET)
    ELSE
    CONTROL ({Retreat Bldg RTU}, {Present Value}, 1, 5, RELEASE)
    END IF

    END

  4. #4
    Join Date
    Nov 2012
    Location
    Upstate NY
    Posts
    16
    Many thanks!!!! I will try when the site re-opens after Xmas. I have to ask, though, why does the Summit application not do this on its own? Seems to me to be a fairly basic feature that most HVAC applications would want. I mean, why does the VAS application activate the AHU Fan Request = 'ON' if it's not going to actually activate the fan?

  5. #5
    Join Date
    Jul 2001
    Location
    maryland
    Posts
    1,355
    Your description of what's going on makes me wonder what's controlling the RTU to "Night Heat/Cool", I've never seen VAS control to 'night heat.cool' so I wonder if Area is taking control of the RTU and it's not responding because it's 'cooling only'.
    Saving the world...one service call at a time.

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