return sizing

sixty7flh

o.k. will TRY and condense this! I took over a 1/2 done home. walls etc already up. I have a bsmt, getting ready to do HVAC. still exposed joists ( ceiling in bsmt) can pan etc.. BUT.. I am thinking of running (3) total returns. (1) will be in the hall, and at the floor, the other (2) will go through the closets ( in a metal duct), then flex in the attic to a high wall grill at my cathedrals.. (1) on each side, as I have a long home, with a greatroom in front, (cathedral), then the hall, other rooms, ( with the attic), and then a master suite ( cathedrals)

1)...what size wall stack/ returns in the closets.

2)...do they make a collar then to transition from that to insulated flex in my attic?
I am putting in a ntrl gas, 90k furnace with a 3 ton a coil, not sure of CFM's at this point... ( i.e. like a 4 ton blower etc..)
I appreciate any feedback!

dan

qbert

You are missing large pieces of the puzzle. A complete Man j should give you heat/ cooling requirements per room then you will know the cfm required. Then you can figure your duct size. With out the proper info you are shooting in the dark! There are plenty of rules of thumb but i would not advise it

sixty7flh

thank you for the info. is a manual J a diy'er? online?

beenthere

You use This to do your own load calc.

Wall stack comes in many sizes. It has to be selected for the amount of air you need to return, and the length of the run for that return.

Termite

Definitely not something you should guess at. Being even slightly wrong can drastically effect the way your system performs (or doesn't perform).