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Old 2013-11-30, 4:22pm
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Speedslug Speedslug is offline
Phill
 
Join Date: Mar 21, 2009
Location: Winnebago, MN
Posts: 2,489
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You want to go over size in your duct work design just to make up for these kinds of things when you can. I had eight inch available so that is what I went with. If I had not used a blast gate I would have need to go to twelve in duct to make up for the losses a dampener flap would have added.

I went with blast gate complete with a frame holding a pulley and picture hanging wire to pull the gate up and let it back down. the wire runs down to a magnet that I move around to open and close the gate. It rattles a small amount when the wind gets really bad. But my house is 130 years old and has all kinds of rattles.

As to terminating the duct work outside, I needed to extend my run along the side of the house and up to the roof line about 12 feet from the hole in the wall to get it away from windows and doors so I turned it upright and put a tin hat on top.
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