Hello,
We are making a decorative range hood that is not possible to have a removable front. There is rigid duct work to just above the insert fan location and was planning on doing a semi-rigid non combustible duct to be able to attach the insert fan and raise it into place.
The builder is telling me this is against code, but I cannot find it anywhere.
Is there more restrictions than 9.32.3.10 that I am not aware of?
And is there another way to have this done?
Thank you
We use a metal flex in new construction all the time to connect a rigid duct to the fan. With some tight spots we just make a custom metal box to adapt to the fan assembly.
Is it the use of metal flex the builder is saying is against code? If so they are incorrect.
The only appliance that requires smooth rigid duct is the dryer.
I figured as much. It is metal flex
They stated that their HVAC guy said it was not allowed and that building inspectors have told them it is not allowed in the past. In our area we have a decent amount of issues with Building Inspectors not knowing what they are talking about so I think the HVAC guy might have just been following what he was told
I pointing them to the article stating as long as it is non-combustible, corrosion resistant, supported etc. then its fine
I am aware it is not ideal, but with a massive plaster hood I do not understand how else to do it, unless there is a sealed telescoping duct I am not aware of.
The only thing they can bother you with is the size.
Table 9.32.3.5 Note 1 says,
QuoteWhere flexible duct is used, the duct diameter shall be increased by 25 mm.
So if you're using 6" rigid duct you technically should use 7" flex. We are never bothered by our inspectors in Ottawa to do this though.
Quote from: Admin on March 16, 2022, 01:53:57 PMThe only thing they can bother you with is the size.
Table 9.32.3.5 Note 1 says,
QuoteWhere flexible duct is used, the duct diameter shall be increased by 25 mm.
So if you're using 6" rigid duct you technically should use 7" flex. We are never bothered by our inspectors in Ottawa to do this though.
They probably don't bother with that one since it implies the entire duct section being flex, but a small, short length as a transitional piece likely doesn't apply.
Yes, good point!
Yes it is about a 3ft run, so I figured it was fine with the size to remain the same.
They still somehow want a large plastered box that weighs a couple hundred pounds to be removable. With moldings and cabinets tied into it