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Thread: VAV boxes

  1. #1

    VAV boxes

    Hey guys
    I have just been given an opportunity to troubleshoot some VAV system for some Shopping mall, but I have no idea how to find some info to educate myself on these systems, so I’m looking for some guidance. By the way the company I work for is one of those that just say figure it out and make it work. (typical……..)

  2. #2
    Join Date
    Feb 2010
    Landis North Carolina
    A Varible air volume system usually consists of a constant blower operation and thermostats controll the vav dampers to open or close depending on temp set point.Some are constant cooling year round and have a means of providing heat at the individual vav boxes so the occupants have a choice of heating or cooling. Or it switch over from constant cooling in summer through chiller to constant heating in winter through a boiler. Also the boxes(vav) are either manufactured as a power open or power closed design and must match what type your controll system utilizes.The vav's can either be powered by electricity or by air(pneumatic)and can be 1 or 2 pipe systems.They either controll an area or can serve individual rooms with own t-stat.So basically you have large volumes of air moving all the time usually in a big loop and the vav boxes feed off this duct to individual vav's to the areas served.So all it has to do is open to condition the space then close when t-stat satisfies. This is a simple overview and im shure I didnt cover everything, but maybe it will give you a start on what you hope to find.

  3. #3

    Confused VAV systems

    I spent some time on the site doing some recon if you will……. And so far I understood that at this store the VAV boxes are fed from a T-stat in the office and the T-stat are receiving temp readings from remote sensors though out the store floor.
    One of the things I did have enough time to figure out was how to know at what position is the damper or flap. And where is it located at. There was a square rod sticking out of the box, witch I’m guessing the was the damper, but there was also two how (1 red, 1 blue) that went from the control box to the 10” duct coming into the box.
    If have done some research online but nothing really shows me a wiring diagram, or a list of the components to the VAV boxes. How do I find out more about this system, because their no wiring diagram on the box itself.

  4. #4
    one of the things i did not have time to find out
    sorry that was a type O

  5. #5
    Join Date
    Dec 2002
    SouthEast NC ICW & Piedmont Foothills
    did you get any info off the box?
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  6. #6
    After so many other techs there is no owner’s manual in or around the box or around the T- Bar. No schematic, well one of them still had the schematic on the control but it’s not legible.
    The only thing I found is the name brand of each component. For example. control board was Johnson control, the air pressure sensor was KGI witch I never heard of. And so on and so forth.

  7. #7
    Join Date
    Mar 2011
    Manchester NH
    You are going to want to make sure that you are getting low voltage from the control board to the accuator as well. Not sure what kind of units they are but we have envirotec units in some of our buildings here and when the board goes then it doesnt send the signal to the accuator to open or close. Good luck

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