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Help, 10"duct through 9" space

Steve88Steve88 Member Posts: 2
Hi all, thanks for the great forum. I have a situation. The heating duct is 10" in diameter, it's been terribly smashed toi fit through a 9" tall by 14" wide space in the framing, then it goes back to 10". What is the proper way to fix this? Is there a fitting for this or what do I do?

Thanks so much.


  • IronmanIronman Member Posts: 3,411
    edited December 2013
    Sheet Metal Shop

    Have a sheet metal shop make two square to round transitions or one double sided one if they can make it wide enough. Or cut out the hole if possible.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • TechmanTechman Member Posts: 2,144
    10 x 9

    Is this for AC also? How many CFM does the space/area require? KindaSorta 300cfm-600cfm thru a 10" round . And a 10" round is equal to a 6"x14" @ .10 static press. A 9"x14" is equal to a 12.25" round or so, I think you would loose velocity. How long is the transition?
  • icesailoricesailor Member Posts: 7,265
    Another way:

    Another way of looking at it is to use two, 9" (or 8") round transitions to 8" X 12" or 14" square transitions with the square part going through the square hole. with the wound duct connected at the two ends. The 9" round is less than 9 Sq. Inches but the square size you can get in will be well over 10 Sq. inches. You could probably buy stock transitional fittings.

    That should eliminate the restriction.

  • Eugene SilbersteinEugene Silberstein Member Posts: 349
    Best vs. Easiest

    The best solution would be to transition, as others have mentioned to an equivalent rectangular duct. The problem with this is that having duct sections fabricated can be very costly.

    A less expensive option, if appropriate for the application, would be to get two 10" round to 12" round adapters, one short piece of 12" round duct and some 12" flex duct.

    If the 12" flex is compressed (flattened) a little to fit through the 9" x 14" hole, you will be very close to your 10" round equivalent.

    Definitely not the best option, but if cost is a major concern, this might be what you are looking for.

    Hope this helps.
  • icesailoricesailor Member Posts: 7,265
    Ducted Clarity:

    For clarity, they make stock sheet metal transition fittings that go from Flex-Duct round to square transitions. You only need two fittings, one for the flex duct on either side of the square hole. You only need a stock transition that will fit through the opening.

    Perhaps some don't realize the connection between round pipes have a smaller area than a square pipe. A 1" pipe has a area opening of .7854 Sq. Inches. A 1"X1" square pipe equals 1 Square Inch.

    Anyone that can knock a piece of tin, should be able to find a metal transition fittings that can be connected together and go through the joist and connect the two round pipes with no restriction going through the square hole.
  • TechmanTechman Member Posts: 2,144
    10 x 9

    How long is the transition? Does the rectangle duct piece require insulation?
  • RJRJ Member Posts: 483

    check to see about a oval duct fitting
  • icesailoricesailor Member Posts: 7,265
    Kind of like this:

    Something along the lines of this:

    They make all kinds of sizes.

    The area of a 10" round duct is 7.854 Sq. Inches. The area of a 3/14" X 10" square opening is 32.5 Sq. Inches.

    That flex-duct is quite squishable. I've seen there installers have run t through a rafter bay from one side of the house to the other. 9" duct in a 2"X10" rafter space, squished between the ventilation pans and the furring strips. In the summer, the heat gain from the roof makes it like heat in the winter when the AC is running and in the winter, like AC when the heat is on.
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