Return Air Grille Size...?
What size is your AC unit, if its 4 ton, you would need two of these.
What size is the return air duct, at the furnace or airhandler? If your ductwork is slightly smaller than the diffuser size, you would have to open up another wall pocket, put a crosspiece at the top of the opening, cut out the bottom plate and connect it to the existing duct. If you are on a slab, do the same thing, only at the top plate. If you want to mount it in the ceiling, its a little different, but you could then use the duct Geo is talking about.
Keep in mind, the size of the diffuser is important, but the size of the duct, volume of air and the static pressure all must be sized to acomodate the other. If the diffuser is on a side wall, it could be 6ft tall and 32in wide, but generaly its only going to be 31/2in deep , and only so much air can pass through that opening. If the main return duct is not sized for a four ton unit, 1600 cfm, it doesnt matter how many openings you have, its not going to work properly.
What size are the supply and return ducts (mains) and what size are the 9 supply branches.
Everybody get your ductilator ready...
Last edited by 8 Ball; 08-16-2008 at 06:15 AM.