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Thread: duct size

  1. #1
    Join Date
    Aug 2006
    Posts
    20
    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 .

  2. #2
    Join Date
    Jul 2006
    Location
    Southern CT
    Posts
    552
    8" duct with volume damper. You can make an 8 smaller, but you can't make a 6 bigger.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    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.

  4. #4
    Join Date
    Aug 2006
    Posts
    20
    where can i look to get the right CFM's for each room i have

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    call your local Pro,or do it yourself for a small fee on this site,click right here;


    http://hvaccomputer.com/talkref.asp

  6. #6
    Join Date
    Nov 2000
    Location
    Memphis TN USA
    Posts
    6,945
    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.
    If the superheat ain't right it ain't charged right.

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