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  1. #1
    Join Date
    Jul 2008
    Location
    Richmond, VA
    Posts
    4

    Running new ducting

    I just bought a house built in 1919 and it has central A/C installed, but I need to run new ducting as the current stuff is not insulated and is coming apart. What size, typically, should I run for the main trunk (downstairs, top-bottom feed, and upstairs) and what size should I run to the individual rooms?

    Here is the basic layout of the house:
    Downstairs:
    Front hall - 10x13
    Kitchen - 12x13
    Living room - 13x14
    Dining room - 13x14

    Upstairs:
    Bathroom - 5x7
    Front bedroom - 13x14
    Back bedroom - 13x14
    Office - 8x11

    It is a typical four-square lay out in the house. Total square footage is 1,351 sq. ft. The unit is barely adequate enough for the house, but it works for now. Should I run 6" flex to all of the individual rooms? All of the rooms, except for the bathroom and office, have two registers in them. The downstairs ones are 2x10's and the upstairs ones are 8"(?) circular.

    Any advice would be wonderful!

  2. #2
    Join Date
    Dec 2007
    Posts
    89
    No Diyers Welcome!

  3. #3
    Join Date
    Jan 2007
    Location
    in my lumpy chair
    Posts
    1,950
    after you calculate the SP, VP, CFM, Area, Throw then you can figure it out.
    read the sight rules no DIYers
    call a pro
    I dont warranty Tinkeritus

  4. #4
    Join Date
    Mar 2008
    Location
    mesa arizona
    Posts
    309

    Cool hey

    sorry guy u need to call a contractor

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    When you look for a Pro,ask" can and will you do a Manual J,S and D ,to determine the load,select the proper size equipment,and design the duct system"??

    Keep dialing ,until you get 3 positive answers,as many can't or won't do these.

  6. #6
    Join Date
    Jul 2008
    Location
    Richmond, VA
    Posts
    4
    I am realizing that I need to get a professional in there to do it right. I just want to know what I need so that way I can tell if the A/C guy is full of BS. I am trying to expand my knowledge so I won't be taken advantage of.

    Thanks for those who have provided some useful info.

    Anything else I should ask of be aware of?

  7. #7
    Join Date
    Jul 2008
    Location
    Richmond, VA
    Posts
    4
    I am realizing that I need to get a professional in there to do it right. I just want to know what I need so that way I can tell if the A/C guy is full of BS. I am trying to expand my knowledge so I won't be taken advantage of.

    Thanks for those who have provided some useful info.

    Anything else I should ask or be aware of?

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,048
    If you want to know what size ducts you need.
    Buy the manuals Dash listed, and study them, then you will be able to figure out what sizes.




    Room size doesn't tell you what CFM a room needs.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Jul 2008
    Location
    Richmond, VA
    Posts
    4
    Okay, thanks!

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