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Thread: VMA1420

  1. #1
    Join Date
    May 2006
    Posts
    665

    VMA1420

    Good-day,

    We have a VMA1420 that is setup for cooling only. This worked fine until modications were done to the AHU which now controls supply air based on OAT.

    Basically, in summer mode the VMA damper will open to cool and close to heat.

    In winter mode, the damper should open to heat and close to cool. But since the VMA is in cooling only, the damper closes when we need to heat up the room.

    Since the VMA doesn't work in this manor (winter mode) how can I change the VMA to open (moduate) the damper in winter to proivde heating.

    In the Q&A no heating is selected.

    Thanks

  2. #2
    Join Date
    Jun 2009
    Location
    StL, MO
    Posts
    583
    HVACpro asks a question (Initiate warmup mode if supply air is much warmer than zone temperature?) that is the answer to yours. If the VMA is not on a network you'll need to add a supply air sensor.

    Another possible option is to configure the VMA with Commercial Zoning Applicatons/Damper Assembly(VMA) in HVACpro.
    UA LU 562

  3. #3
    Join Date
    Mar 2009
    Location
    Several Miles from Sane
    Posts
    1,459
    Assuming the VMA is pressure Independant you can get it to do what you want...sort of.

    You need to write JCB/GPL so that when the AHU goes into "Heat" you command the VMA first to Unoccupied then to "Warmup", the warm up is a Box Mode function. Make the warm up CFM setpoints about 1/2 of cooling setpoints to start with. The key is in the Supervisory controller logic so you don't over heat the space.
    If sense were so common everyone would have it !

    All opinions expressed are my own. Any advice provided is based on personal experience, generally accepted fact or publicly available information. As such, it is worth exactly what you paid for it, not a penny more not a penny less !!

  4. #4
    Join Date
    Mar 2008
    Location
    NW Ohio
    Posts
    949
    Try it config'd as CZA.

  5. #5
    Join Date
    Dec 2009
    Location
    Canada
    Posts
    39
    I didn't think the CZA supported pressure independant control. Haven't used it in a while though, so I'm not really sure.

  6. #6
    Join Date
    Mar 2008
    Location
    NW Ohio
    Posts
    949
    Quote Originally Posted by DreamCar View Post
    I didn't think the CZA supported pressure independant control. Haven't used it in a while though, so I'm not really sure.
    Yes, it doesn't..........and?

  7. #7
    Join Date
    Dec 2009
    Location
    Canada
    Posts
    39
    Quote Originally Posted by NINAX View Post
    Yes, it doesn't..........and?
    If my recollection is sound (a big if...) you can't download a pressure dependant sequence into a VMA-1420.

  8. #8
    Join Date
    Mar 2008
    Location
    NW Ohio
    Posts
    949
    There seems to be a around trend here, more and more "I don't know, but" and "I've never used one, but"....

    Not specifically directed at anyone, just a general observation.
    Attached Images Attached Images  

  9. #9
    Join Date
    Dec 2009
    Location
    Canada
    Posts
    39
    Quote Originally Posted by NINAX View Post
    There seems to be a around trend here, more and more "I don't know, but" and "I've never used one, but"....

    Not specifically directed at anyone, just a general observation.
    Right you are, I should have checked before posting. It was late & I wasn't at my work laptop. Just lazy!

    This is however an open forum for discussion, and I for one would rather know the poster's level of confidance in their answer than assume they're 100% sure.

  10. #10
    Join Date
    Mar 2008
    Location
    NW Ohio
    Posts
    949
    Quote Originally Posted by DreamCar View Post
    Right you are, I should have checked before posting. It was late & I wasn't at my work laptop. Just lazy!

    This is however an open forum for discussion, and I for one would rather know the poster's level of confidance in their answer than assume they're 100% sure.
    We're on the same page.

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