FLEXIBLE DUCT FOR PLENUM CONNECTION???

[tcihvacff1]

Hello Everybody!
Good Day!!!
With reference to the subject I am dealing with duct work on site wherein I found discrepancy in the design & its as follows:
A DUCTED FCU of capacity 396 l/s with a duct size 700X150mm & the distribution of air to the living/dinning room is via a Diffuser(225x225mm-50 l/s= 2Nos) & a Linear Air bar grille of size 1500x100mm for 296 l/s air flow. The designer has selected 200mm flexible duct to connect it with the Plenum of linear bar grille in 4 Nos of multiple connections whereas the Main rectangular duct height itself is 150mm, hence I can't fix 200mm flex duct in a 150mm height of duct. illogical!

At this moment I cant even re-size the main rectangular duct as all the shop drawings are processed for duct fabrication.
Should I go for a 100mm flexible duct by increasing the Nos of multiple connections or I need to increase the size of a plenum?

I am worried about Noise level.

Please advice. Your comments are highly appreciated.


Thanks in advance.

 

[willard3]

Check SMACNA, toy can fabricate a transition from the rectangular duct to other shapes/sizes.

https://law.resource.org/pub/us/cfr/ibr/005/smacna.duct.1995.pdf

 

[317069]

Can't you connect the flexible 200 mm duct to the top of 700x150 mm duct instead of the side?

 

[dbill74]

You should be submitting this question in the form of an RFI and possible change order to your designer of record. He will need to sign-off on any deviations from plan.

 

[tcihvacff1]

dbill74 you are correct. I sent them a RFI but our consultant is damn good you know....After trying that I posted here.


@317069 (Mechanical) I think its ok. but if I connect flex from the top then the balancing(round)damper will be in a vertical position which is again a issue.
And also the flex duct will be in a C-Shape.

I will check once....or else I will resize the plenum.


Thanks all.

 

[emalsyd]

You should be able to make a side takeoff rectangular to round transition with a 45* entry. Have them make it 150mm on the side then transition to 200mm round.