First off, I'm new to the site, so if this an ignorant or inappropriate question, I apologize up front.
I have a two story house with a basement. It presently has boiler heat that went out this spring and window unit AC.
I have been flirting with the idea of having a central heat/AC unit installed, but cannot imagine how the ducting would work. Due to design issues of the house, there is a large area of the second floor that has no access by way of interior wall voids. There is, however, dropped ceiling in most of the first floor and a large closet I can steal for vertical.
My question is: (placing the unit in the basement) Is it possible to have one extended plenum in the basement serving the first floor floor registers and a plenum that rises vertically to the void in the first floor ceiling, turns and runs horizontally through the dropped ceiling and branch off from there to serve second floor floor registers? Or just end the vertical in the void and run branches directly to it? Or maybe run several separate branches up through one chase? (Is there a limit on branch length?)
I'm just trying to picture in my head how this would work. I'm sure a second unit in the attic would be ideal, but that is FAR out of the price range.