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  1. #1
    Join Date
    Jan 2009
    Location
    Massachusetts
    Posts
    181

    American AutoMatrix VAV pressure dependent VAV

    We have a retrofit project with pressure dependent VAV boxes. I'm going to use NB-VAV.
    My questions:
    1. Do I need a supply sensor for this type of application?
    2. In the manual I see that damper position based on estimated flow (there is no flow sensor in the box). I don't understand how to configure the controller in NB-Pro if I don't know max flow. Is it possible to configure control based strictly on space temperature signal (cooling)?

  2. #2
    Join Date
    Jul 2009
    Location
    From the pacific coast, live in the mid-west now!
    Posts
    74
    Quote Originally Posted by eparizher View Post
    We have a retrofit project with pressure dependent VAV boxes. I'm going to use NB-VAV.
    My questions:
    1. Do I need a supply sensor for this type of application?
    2. In the manual I see that damper position based on estimated flow (there is no flow sensor in the box). I don't understand how to configure the controller in NB-Pro if I don't know max flow. Is it possible to configure control based strictly on space temperature signal (cooling)?
    1. nope - if you see a supply air setpoint somewhere, set it to 999.0 to lock it out and set the supply temperature object's OutofService to true. Supply sensors are optional in the VAV, just like ASC RTU/HP/FCU applications and can stop things from working too just as easily if you don't have or need one.

    2. yes - you need to set the Damper Control Mode (under Flow Control) to Presssure Dependant mode. When we did this, we also had to set our cooling flow setpoint and the prop-band/integration values. These values seem to affect how the damper open and closes even though you're not using the onboard flow sensor. I still dont understand why they need set, but once you have them set, it works flawlessly.

  3. #3
    Join Date
    Jan 2009
    Location
    Massachusetts
    Posts
    181
    Thanks!

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