I have several questions related to my Goodman Furnace (Model GMS90703BXA - 69K BTU / 93% efficiency), which is installed HORIZONTALLY in the attic and SUSPENDED about 14" from the attic floor in one long line as follows: [right to left] return plenum (3' wide x 14" tall x 24" deep) / furnace / spacer duct (12" long ) / A Coil / supply plenum (2 pieces: one 4' wide and one 2' wide; both x 21&1/2" tall x 16&1/2" deep)
Duct Placement ?
I have at least 8 flexible ducts to attach to the supply plenum (two 4"; five 6" and one 12" which will supply the basement ducts) and at least 2 large ducts to attach to the return plenum (one 12"; one 10 " which runs to the basement). What should I keep in mind when mounting my flexible ducts into the supply plenum? For example: where should they be placed relative to a bypass humidifier (see question two)? Does it matter whether they are mounted on the top / bottom / end of the plenum? Should they be equally distributed (by air volume) on opposite sides? Should they be mounted down the center line of the plenum, or slightly above/below, or staggered on either side of the center line? Have I missed anything?
Humidifier Placement ?
I have a Honeywell Bypass Humidifier (model HE220A) and the installation instructions are very conflicting. Which plenum should I install the humidifier in AND what is the ideal location on that plenum (considering the relative position of the supply ducts). Obviously, the 6" bypass duct will install on the opposite plenum, but I'd also like to know if there's an ideal installation location for it as well (again, considering the relative position of the return ducts). Have I missed anything?
Insulation Effectiveness ?
Lastly, what is the most cost effective way to insulate my attic mounted HVAC system? Should/can I wrap the furnace and/or plenum(s) If so, with what? Or is it more effective to insulate in between the rafters? Or should I use a stiff insulated/reflective sheet mounted across the rafters? Is there an ideal combination of treatments? Also, I'd like to suspend some of the insulated flexible duct (to maximize floor space for storage). Is that a bad idea? Have I missed anything?
Thank you in advance for your time...
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