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  1. #1
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    vav and balancing



    Chaps

    have we any air balancing experts here??

    Got asked to tender some air balancing and verification prior to a refit. The total air needs confirming and each unit tested. The site has 25 VAV units as per pic.

    How long would you expect to spend both in money and time as I have to give approx by this weekend :-(

    vent.JPG



  2. #2
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    Re: vav and balancing

    you have to allow for leaks in ductwork, and bodges where theres open ducts in the roof space, also the ahu will be operating on a supply air pressure transducer and inverter so you would have to fix the supply fan to give a fixed output and ur vav 's are adjusted off a maximum/minimum regulatin valve, you will find tubes popped off and if the system does heating, the bellows cook and air rattles through as the bellows wont deflate properly
    http://www.mediafire.com/view/?6y54s03g5gbzc4g

  3. #3
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    Re: vav and balancing

    Great stuff but I need budgets. I was thinking 1/2 hr per VAV box + 2 days for the system. It all looks old and tired though...


    DSC05464.jpgDSC05465.jpgDSC05466.jpgDSC05469.jpg

  4. #4
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    Re: vav and balancing

    and the rest, as you will need to recheck them, also ceiling tiles should be refitted as usually ur return air is ur void

  5. #5
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    Re: vav and balancing

    Quote Originally Posted by install monkey View Post
    and the rest, as you will need to recheck them, also ceiling tiles should be refitted as usually ur return air is ur void
    Ok will double my estimate and see what they say :-)

  6. #6
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    Re: vav and balancing

    From my limited experience of once on same type of job but bigger I would allow 1.5 days for the vavs and 1/2 day for the ahu with two guys of course = 4 days, plus 1/2 day to write report and present spread sheet then add a day for the safety factor.
    AHU need to measure with fan at 100% with all vavs 100%, 100% return, then 100% fresh, both filter and coil velocities and area for calculation. Normally expect 10% leakage. Measure static at index (last box), fan statics, plenum statics, fan r/m etc.

  7. #7
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    Re: vav and balancing

    Quote Originally Posted by Tesla View Post
    From my limited experience of once on same type of job but bigger I would allow 1.5 days for the vavs and 1/2 day for the ahu with two guys of course = 4 days, plus 1/2 day to write report and present spread sheet then add a day for the safety factor.
    AHU need to measure with fan at 100% with all vavs 100%, 100% return, then 100% fresh, both filter and coil velocities and area for calculation. Normally expect 10% leakage. Measure static at index (last box), fan statics, plenum statics, fan r/m etc.
    that works out roughly what i allowed so my guess is reasonable - bet my price won't be ;-)

  8. #8
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    Re: vav and balancing


  9. #9
    Brian_UK's Avatar
    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
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    Re: vav and balancing

    Looks like a nice leaky pneumatic system to play with, have fun with it.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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