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Please advise if you see any issues with the duct/vent being installed for my kitchen vent hood. I have ZV950SDSS Monogram® 36" Wall-Mounted Vent Hood to be installed in the kitchen. The installation manual calls for a 8" duct size with a maximum equivalent duct length of 100'.
In my case, the duct to the outside wall of house is 11 ft away from the kitchen. From there the duct is transitioned into 3-1/4" * 12" straight duct into the kitchen wall. As you can see the duct had to move to the right, the builder has turned it further to position it where it should be. This has introduced an other turn at the end of the straight duct. I would imagine he will connect the hood with an other 90 degree elbow.
Ideally I would expect a duct to the ceiling , 90 degree elbow into the ceiling and running it 11 ft to the outside wall have lesser turns than what I see in my case. With all these transitions and turns, do you see it is exceeding the maximum duct length of 100'? Is there an easy way to fix this?
Regards,
Chip
Last edited by csrikanth; 10-07-2016 at 10:35 AM..
Well I'm certainly not going to do the math for you- the "formula" is right there on the third pic you posted.
The better question is- does the HVAC contractor that ran the duct work know the type/model of venthood you're using? And do they have that same sheet? An another question would be- "does the requirements of the manufacturer meet or exceed the requirements of the AHJ?".
Thank you for the reply. Attached is the closer look at the vent with turns. I would imagine there will be an additional 90 degree elbow to fit into the hood. Problem is I don't see the exact turns in the manual so I am not sure how much I need to take away at each of these turns in arriving at the equivalent length. Do you see this is exceeding 100 ft? overall is this duct looking ok? Please see the attached picture.
Is it just me or are few of the 2x4s attached to each other square and level? It appears some fire stop 2x4 members are too short to span the width of the stud bay. All 2x4 framing members should be cut so that they are held in place via compression before being nailed.
In the "Duct work for kitchen vent hood front.jpg" there's a notch in the horizontal fire stop (right above blue gang box). That shouldn't be there or it needs to be filled in with expanding fireblock foam.
The double top plates were cut away to allow for the ductwork. Is this wall load bearing?
Is there a reason why the rectangular part of the ductwork needed turn #2? Why not run the ductwork on a slight diagonal (esp. since it's ****-eyed already)?
[Edit: lol, C-D bleeped the word that rhymes with clock-eyed]
Note: add 2'6" for each 45 degree angle (a 90 degree = 2 x 2'6")
Last edited by James1202; 10-08-2016 at 01:42 PM..
Reason: censorship explanation
I wouldn't second guess your contractor. You should ask him/her directly. These are his subs and he's the one who has to pass inspection. However, if you're not satisfied with a kitchen vent/exhaust... really? That's the least of your worries. Does he have other homes that are completed and occupied with the same configuration? Wonder if there's a problem.
Sometimes I like to put the 100' thing into perspective. Generally, each "story" of a building is 10'. So 100' is the height of a 10 story building. You're probably okay with distance. Ducting specialists can figure out how the turns, bends and reductions affect your airflow.
The fittings pictured conservatively would equal 60, 80, 60 + the duct length, + the termination cap, + connecting fittings. I say conservatively because the figures usually double when you stack one fitting after another when there's no linear space for the air stream to straighten out. What you'll be left with is a 700 cfm hood that doesn't move near the air it's intended to and will rumble excessively.
Edit: also, where is the 700 cfm of air coming from? What goes out must come in...hopefully not thru a w/h flue.
Yep, I'd forget all about the ductwork at this point and have them figure out how their going to support those two TJI's that end over that spot.
I just love it when HVAC rough techs work with their head up their ass!
Once the sheetrock is up, you won't be able to see that stuff so it won't matter. /sarc
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