vav and balancing

[r.bartlett]

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 :-(

10042

[install monkey]

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

[r.bartlett]

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...


10043100441004510046

[install monkey]

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

[r.bartlett]

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 :-)

[Tesla]

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.

[r.bartlett]

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 ;-)

[install monkey]

http://books.google.co.uk/books?id=NR8HNQq9wQoC&pg=PA205&lpg=PA205&dq=balancing+a+vav+system&source=bl&ots=evYBjdCynH&sig=_wBkG9QioKdXQ8ijAtyRPqvi2qE&hl=en&sa=X&ei=gs0XUZfqN4qM0AWf34DIBQ&ved=0CDIQ6AEwAA
found a link that may be of use

[Brian_UK]

Looks like a nice leaky pneumatic system to play with, have fun with it.