new room supply and return - http://www.hvacmechanic.com/ Forums
Original message
| james
 |  "new room supply and return"
, posted Tue 4 Nov 14:02  
Hi all!
Need some help making sure the supply and return to a new room over my garage is sufficient before committing to it and finding out trouble later when it is too late. My home is a bungalo basically square and 2600 sqft (basement and mainfloor). The new room is 370 sqft with two windows 4ft x 6ft. I have a Lennox 90UGF-75 furnace. The current main supply size in the center of the basement where I wish to branch from is 8" x 16". I was thinking to use two 6" round feeds from the main branch but thought I ahould check first in case it should be different. The distance from the main supply to the new room windows is 32ft and 37ft.
I was going to have one return in the floor opposite the windows in the new room between the floor joists.
Not sure if this is enough info.
Thanks for any help with this.
dimer
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Replies:
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| Ad Mech
| "Re(1):new room supply and return" , posted Thu 6 Nov 21:04
Dimer
Missing some info
After the 75 on the model number there should be a single digit number. like 3 or 4. this is tonnage of air flow.
three means 3 ton or 1200 Cubic Feet per Minute
We want about 100CFM per outlet.
count the supplies you have now
if you have 12 and a 3 on the model number and add two more runs, the airflow to all the supplies will be less.
The furnace will be undersized and run longer..can you live with it
maybe.
if it is a four ton with 12 supplies you will feel a lot of air coming out each register then go for it.
good luck
Dave
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