Need Help Sizing Cold Air Return

[El Finko]

Help guys. I'm sizing a cold air return for my 1450 sq ft rancher. Stove is in basement. Hot air will rise through registers around perimeter of house. Cold air will return to stove via one main duct centrally located.
Question: based on 1450 sq ft, what ballpark am I in as far as duct diameter (I'm thinking round is easier) and fan cfm??
Any thoughts appreciated.

 

[begreen]

That is the opposite of what usually works best. The returns are usually on the outer walls because the air will natural be sinking down along the colder outer walls. The supply is usually central for the rising hot air. If you look at old gravity fed coal systems, this is the way they were installed.

However, before cutting any holes be sure to consider other options like moving the stove where the heat is desired, upstairs. And be sure to check local code. Often the registers will require fusible link fire dampers Remember that you are essentially creating a chimney system. If something catches fire in basement this system will fuel the fire quickly with a lot of air. Code also may set the distance the stove must be from the central grille in this case to no less than 10ft.

 

[El Finko]

I hear you BG. Thanks for the input. Can't move the sotve, though. And I was thinking about the simplicity of one return duct versus a whole system of ducts spreading throught the basement.
What is a fusible link fire damper?
Anybody have any thoughts on estimated duct sizes and fan cfm? To clarify, the house is 1450 sq ft up and 1450 sq ft in the basement- 2900 total. Thanks

 

[begreen]

Why are you ducting this? Is the basement an open space or is it a series of rooms closed off from one another? If it is relatively open, no ducting needed. The area itself will act as a duct.The perimeter returns don't need to be large, 4"x12" should be sufficient for smaller rooms. The supply is the one that needs to be central and large.

Fusible-link damper info:
http://www.greenheck.com/media/pdf/catalogs/LSDApplSelection_catalog.pdf
http://www.atlantasupply.com/swscri...O_@&MDL=12AH*&JCAT=12AH&REQUEST_ID=QCSTLST_AS

 

[El Finko]

Basement is open, but stove is fixed in one corner. Cannot change that, unfortunately. The upper floor (rancher) is the one that's all chopped up- nine separate rooms. I'm thinking that hot air spread evenly around basement will get up to individual rooms better if each room has it's own delivery point.
Cold air could then migrate to the middle of the middle-most room upstairs, where it can be sucked back down to basement and delivered straight to the corner where the stove is.

 

[El Finko]

I was also thinking that having a constant stream of cooler air blowing across the stove would help to regulate temps.

 

[begreen]

These ideas are fighting nature. Regulating the stove is in the domain of the operator.

 

[El Finko]

I don't think I'm fighting nature. I'm just not relying on gravity.
Hot air chases cold air. I'm drawing the cold air from the middle of the house back down to the stove....
Where it will be heated...
Then it will chase more cold air up through the registers. Voila! Circulation.
So the key variable becomes duct size and fan cfm. Anybody have any ideas or know where there might be an online calculator that might get me in the ballpark? Not looking to be spot on, mind you.
BG, thanks for the links on the fusible links. I will definitely use those.