New to this board, and to ducts... I've been doing my own electrical wiring and some plumbing for a long time, but have no experience with ductwork. My 6BR, 4BA house HVAC is, to put it mildly, a mess. There is a wood furnace, and also a gas furnace and older Carrier a/c. Two manually operated dampers on the output plenums select which system is in use. The intakes are both connected to the return duct, but badly. There are four small returns scattered almost at random. See the pictures
Recently I started to remove the tub and floor in one of the bathrooms to fix soft spots. Among other interesting "fixes", when central heat/ac had been installed, to make room for a small return in the hallway they cut the joist (that ran directly under the tub, naturally) and set each end on cinderblocks directly on the dirt crawlspace. Having no codes/inspections is a mixed blessing... but I digress.
Anyhow, in order to structurally repair the floor and reinstall the joist properly, I had to remove that return duct. I now want to have one large return, with a filtered grille, in the wall at the end of the main hallway. Behind that wall is a walk-in closet, and it's nearly a straight drop through the closet floor to the return duct. To start with, I need a grille and filter assembly, preferably 14" wide or less, so that it will fit between the studs without framing an opening. I was thinking of a 25x14 mounted with the long dimension vertical.
But then I need to connect to the duct passing through the floor, which means a 90 degree elbow. Is this something I'll have to make from sheetmetal, or is there a standard piece that I can buy?
It would not be too much more trouble to frame in a horizontal opening in the wall in order to mount the 25x14 horizontally. Once I get it into the basement I'll worry about how to connect it to the return trunk next...
When the return is functional I'll attack the supply ducts next. Any tips and tricks greatly appreciated. There are few contractors in my area, I don't know how qualified they are, and I would rather learn and do it myself while saving money...