duct size

[gmcwelder]

can anyone give me the room size for 6" duct and 8" duct.say i have a 10'x10' room , would you use a 6 or 8 inch duct .

[psychometric]

8" duct with volume damper. You can make an 8 smaller, but you can't make a 6 bigger.

[dash]

You need a room by room load calc.,Manual J,to determine the cfms(air flow),to then determine the duct size.

Anything else is just a guess,including "rules of dumb".
"
We have 10X10 rooms that need a 5" to an 8", round duct.

[gmcwelder]

where can i look to get the right CFM's for each room i have

[dash]

call your local Pro,or do it yourself for a small fee on this site,click right here;


http://hvaccomputer.com/talkref.asp

[kim]

3000 BTU = 100CFM. That should be a 6" pipe if the total equivelent length is not too long.

What is the load on that room?
Does it have lots of windows?
Does it have 3 sides exposed to the outside? etc.