Cooling from basement to second floor?

[hugh67502]

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.

[hcong]

It depends on how big your wall void is... if you can fit a duct in the void that is big enough to supply air to your second floor, else I would do the Chase idea. Try to keep the ductwork as simple as possible, avoid take offs from branches (higher static pressure loss), and don't forget how you are going to duct your return.

There is no limit in length, you take the longest duct run for your static pressure calculations. The more complex your ducts the bigger you fan needs to be.

[beenthere]

In general, yes its possible. don't know if your drop ceiling is low enough for it though. It would be a good way to do it, as you could also have a zoning system installed at the same time, so each floor could be controlled independently of the other.

[hvacvegas]

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.

I think you'd be suprised at the price of running all new ducting in an existing house. Especially up to the second floor.
Not just the cost of the HVAC installation, but also for the drywall repairs, possible reframing to allow duct installation (rare).

[hugh67502]

Thanks for all of the replies!

hcong - The ceiling is dropped about 12" and I have a huge central area for a vertical run, so I don't think space would be a problem.

hvacvegas - I'm an electrician, so I'm aware of the costs of hiring a highly trained professional to perform a professional installation.

beenthere - what is this "zoning" you speak of? I'm not aware of this or how it works..

[beenthere]

Motorized dampers are installed in the 2 trunk lines, a zone panel is installed to control the furnace and A/C. Along with a thermostat for each zone/floor. When the upstairs needs cooling, even if the first floor doesn't, the zone panel brings on the A/C and closes the damper to teh first floor, so it doesn't over cool.