Original message
| psay51
 |  "Plenum for gas furnace"
, posted Wed 7 Nov 08:00  
My Bryant furnace is rated at input: 88,000 BTU/Hr, and output 71,000.
The supply air opening for the plenum is 19"x13", and I have 24" headroom for height, which is plenty to attach the five existing 6" round pipe ducts. But is it large enough as per any possible manufacturer's recommendations or safety concerns?
Also, the opening has about a half inch vertical lip all around - obviously for attaching the plenum. What is considered a correct/good way of doing that? Any seal required, or just metal to metal with screws?
Again, thank you in advance.
peace
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Replies:
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| Hube
| "Re(1):Plenum for gas furnace" , posted Wed 7 Nov 09:54
Put "S" clips on these lips and then place the raw bottom edge of the plenum into these "S" clips, and metal screw.(caulk corners)
A heigth of only 24" is borderline, (30-36" would be best)but you could also extend the plenum a foot or so HORIZONTALLY if possible.
ex; 13 x 19 vertically to 10 x 19 horizontal, and tap in your takeoffs into the side/top of this horizontal section of "extended" plenum.
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| | psay51
| "Re(2):Plenum for gas furnace" , posted Wed 7 Nov 13:11
Thank you much, Hube. If you don't mind:
a) I do not quite understand what you meant by "ex: 13 x 19 vertically to 10 x 19 horizontal".
-- I am now at 13"wide, 19" deep (front to back) and can go 24" high.
b) I can expand to one side by 8" to 21"x19"x24"high, which would bring the total volume of the plenum to about 5.54 cubic feet. That would be like raising the height of the original 13x19 to about 39" which would produce about 5.57 cubic feet. ( a 13"x19"x36" would be about 5.15 cubic feet). I figure that is what you had in mind.
c)I am glad I asked about this, and now I wonder why the size is so important. I would guess it has mainly to do with the amount of air it is designed to move and heat the unit produces per time unit.
And thank you again.
peace
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| | Hube
| "Re(3):Plenum for gas furnace" , posted Thu 8 Nov 09:52
The plenum size of 19 x 13 is no problem. It is the heigth that is questionable. IF possible, a 90 degree turn to 10 x 19
(square throated extention ) (picture the letter "L" upside down) would give the air a chance to get rid of any turbulance,etc cause by being too close to the units heat exchanger before being forced into the small takeoffs.(this extra extention will help eliminate any air flow stratification.
Otherwise, if this extention cannot be done then make sure you keep any takeoffs as high as possible.
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