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Re: insualation clearance from draft hood
"The way I understand it Jerry is according to the vent connector sizing charts, all offsets begin with a 1 ft(12") rise."
That I am aware of. Don't always see it, but know it should be there.
"As for the clearance, The 1" clearance is afforded by the double walled section of the B-vent."
That part I got too.
"Therefore, any part of the vent including the single walled connector below the insulated portion and including the draft hood proper would carry a 6" clearance. Let's say you have a draft hood connector attached to B-vent and the distance from the insulated portion of the B-vent to the widest part of the draft hood where the air enters is 5"."
Okay, that's getting to what I was asking about. That lower, wide, part of the draft hood, you measure out 6" from it, right"
"Then this 5" section carries a 6" clearance."
As measure out from the widest part and sloping in as the draft hood size reduces?
"However, once you reach that first roll in the Bvent, it drops to 1"."
Yep, that I also have down.
"So, from the opening inlet of the draft hood up about 5" I then measure 6" from there would mean the lowest combustibles could reach down a pipe toward the draft hood would be about 11-12"."
Okay, do you measure 6" out from the wide part of the draft hood, as though you were sliding a cylinder over it? Or, does your measurement taper in to match the profile of the draft hood, only you are measuring 6" wider?
"You have to remember this clearance is measured by swinging arcs so the single walled portion of the draft hood, which carries a 6" clearance is not measured perpendicular but tangential in all directions. This means the first 6" of so of the B-vent actually must be at a 6" clearanc for the single walled connector under it."
Got that too, but what about the questions I have above?
Let's say the draft hood is 6" wide at the bottom and 3" wide at the top, with the transition being 45 degrees.
You would measure 6" out from the bottom, at the bottom. This means an 18" diameter circle.
You would measure 6" out at the top, from the top (including up 6" from the bottom of the B vent). This means a 15" diameter circle.
And the space between those two are measured out to that 45 degree slope. Meaning the 6" clearance circle goes from a 15" diameter to an 18" diameter at a 45 degree connecting slope.
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