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Old 12-31-2010, 05:54 PM   #1
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range hood, two dampers in cold climate?


Hi all,

I'm starting to install a wall mounted canopy range hood and in reading the instructions I'm confused on a couple points. Firstly there is an instruction stating that if the wall cap (I'm exiting through the wall) has a damper, then don't use the one included in the hood. The one on the hood is just above the squirrel cage fan. Later, a new instruction under the heading of "cold weather installations" mentions that an additional back draft damper SHOULD be installed. In that paragraph it also mentions using a thermal break. Can someone firstly tell me if I should use both dampers (I'm in Toronto, so yes it's cold weather a lot of the time) and also what I should be looking into for thermal break in the duct. I'm using 6" round duct for this.

THanks all!!

Zantar.

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Old 01-01-2011, 12:54 AM   #2
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range hood, two dampers in cold climate?


May get replies here in the Appliance forum.

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Old 01-01-2011, 10:28 AM   #3
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range hood, two dampers in cold climate?


good idea
Thanks.
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Old 01-01-2011, 12:02 PM   #4
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range hood, two dampers in cold climate?


Toronto is not cold all of the time, but if it was me, I would use both, or just install without the outside damper, see how it goes this Winter, and if it seems that the unit damper is not keeping the cold air from coming back through the unit into the house, then install the outside damper unit by next Winter.
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Old 01-01-2011, 01:52 PM   #5
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range hood, two dampers in cold climate?


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Originally Posted by gregzoll View Post
Toronto is not cold all of the time, but if it was me, I would use both, or just install without the outside damper, see how it goes this Winter, and if it seems that the unit damper is not keeping the cold air from coming back through the unit into the house, then install the outside damper unit by next Winter.
Yes- I'm leaning now towards using both dampers.

Do you know anything about this thermal break? I'm thinking about some PVC if it will fit. I assume the temps are not too high (fire hazard) as the part that comes with the vent that attaches to the squirrel cage is in fact plastic..

Also, for the joints I'm thinking sheet metal screws and aluminum tape. Makes sense?

What about the insulation around the vent through the wall? Mineral wool is okay?

Thanks!
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Old 01-01-2011, 02:04 PM   #6
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range hood, two dampers in cold climate?


Follow the instructions. Use Metal duct, not PVC. As for Screws, they will secure the duct to the hood and outside part, but Aluminum tape helps to seal the joints, same as mastic for duct work.
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Old 01-01-2011, 05:14 PM   #7
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range hood, two dampers in cold climate?


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Follow the instructions. Use Metal duct, not PVC. As for Screws, they will secure the duct to the hood and outside part, but Aluminum tape helps to seal the joints, same as mastic for duct work.
I would be using galvanized metal 6", but I'm curious how to create the thermal break that they recommend. Unfortunately they make no mention of how to create the thermal break (what type of part etc). I just thought a short piece of plastic, the right diameter might do the trick. Maybe a 3" stretch just near the exterior cap. Do you know what part to use for this?

Thanks.
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Old 01-01-2011, 05:51 PM   #8
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range hood, two dampers in cold climate?


You can't use plastic on a range hood. It has to be metal. As for the Thermal break, that is what the Dampers do.
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Old 01-01-2011, 08:02 PM   #9
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range hood, two dampers in cold climate?


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You can't use plastic on a range hood. It has to be metal. As for the Thermal break, that is what the Dampers do.
Well, it's a bit confusing because the instructions say to add an additional damper and a thermal break:

"An additional back draft damper should be installed to minimize backward cold air flow and a nonmetallic thermal break should be installed to minimize conduction of outside temperatures as part of the vent system. The damper should be on the cold air side of the thermal break"

Also the shroud that connects the duct pipe to the opening above the fan is plastic (this came with the unit).

Anyway, at this point I'm probably just going to go with the metal.

Thanks.
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Old 01-31-2011, 10:39 AM   #10
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range hood, two dampers in cold climate?


Zantar,
could you please post the results of your instalation? Did you find a solution?
I have the same problem and after installing the downdraft vent w/o the thermal brake and with only the damper included with the vent, I find a thick layer of ice on my glass cooktop - I am afraid to use it !
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Old 01-31-2011, 11:17 AM   #11
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range hood, two dampers in cold climate?


Ice on the range - wow.
Try to go with 2 damper setup.

Problems I've seen with range hood dampers is a tendency to not open close very freely - especially the outer one going to the outdoors.

Gunk buildup is one cause, undersized fans are another - it doesnt have the power to blow open both dampers.
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Old 01-31-2011, 12:13 PM   #12
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range hood, two dampers in cold climate?


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Zantar,
could you please post the results of your instalation? Did you find a solution?
I have the same problem and after installing the downdraft vent w/o the thermal brake and with only the damper included with the vent, I find a thick layer of ice on my glass cooktop - I am afraid to use it !
Hi. I ended up not doing the thermal break. I did install both dampers and I'm glad I did. So far it's working quite well. The underside of the metal filters is cool to the touch, but not icy. I wonder about some sort of insulative wrap for the section of pipe inside the house.. Something like that must exist.. Also, it occurs to me that a HRV designed for range hoods should be manufactured. Something else to look into

It never ends..
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Old 04-13-2011, 08:19 PM   #13
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range hood, two dampers in cold climate?


Hi Zantar, I'm from Alberta and we had a range hood installed last fall. The only damper is the one on the unit itself. The vent is about 3 or 4 feet straight shot out the roof.

We have two issues:
1) in windy conditions, the damper on the range hood flaps like a flag. Very noisy.
2) When it is cold, we get condensation from the range hood falling onto the cooktop.

So I can see why a thermal break would be advantageous. We are going to get a new vent cap (goose-neck) installed on the roof with it's own damper. Hopefully that will help with both our problems.

If not then I too am wondering how to create this "Thermal break".

Thanks for posting your experiences.

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