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Thread: Duct Shapes

  1. #1

    Duct Shapes

    Hi

    1) Why we prefer that duct shapes should be square?

    2) Whats the difference between circular shaped ducts and square shaped ducts , i mean where we will prefer circular shape and where we will prefer square shape ducts?

  2. #2
    Join Date
    Oct 2010
    Location
    SW Michigan, near Battle Creek
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    921
    square shapes fit over ceilings and match up with square equipment better. they are easier to hook different sizes together. round would be more efficient in every way if it would fit.

  3. #3
    Join Date
    Mar 2003
    Posts
    7,326
    Rectangular shaped ducts have a way of being easy to layout and install as opposed to round or oval. As noted, above ceiling is a consideration on any project, especially larger commercial jobs requiring lots of airflow. Every trade knows that there will be a duct somewhere that they have to miss with their pipe, wire whatever.

    In commercial real estate, area of the occupied space is treated like gold, so ceiling heights, mechanical room sizes etc all come in to play in calculations of rent, utilities etc in terms of price per square foot.

  4. #4
    Join Date
    Dec 2007
    Location
    Bucks County, Penna
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    181
    Round duct is a pain in the butt if it gets squooshed a bit at the shop, on the truck, or hanging around the job site before it gets installed. Rectangular duct is stronger.

  5. #5
    Join Date
    Mar 2009
    Location
    VB
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    322
    I ditto everthing except
    Rectangular duct is stronger.
    Double wall spiral duct is pretty stout also.
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  6. #6
    Join Date
    Dec 2007
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    Bucks County, Penna
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    181
    I never installed double wall spiral, so I'm ignorant about it...

    Round duct is also easier to take apart to clean or replace than rectangular would be, such as from an oil burner, especially for a typical home owner to do themself.

  7. #7
    Join Date
    Jan 2006
    Location
    Virginia Beach, VA
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    12
    Nice Striper Duece! Is that picture recent?

  8. #8
    Join Date
    May 2007
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    Dry as a bone Tucson
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    4,509

    SQUARE

    Square duct has less resistance to airflow, is cheaper to make, and more economical to install.
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  9. #9
    Join Date
    Nov 2006
    Location
    SC
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    930
    Square is easier to custom fab in the shop.
    Rectangular is low profile
    The shape matches the air handlers
    Both look more expensive than round

    Round provides the least friction loss
    You can fit more on the truck
    It's generic, and you can buy it in bulk
    It's fast
    It is available to any hack without a shop and therefore sometimes has a bad name.

  10. #10
    Join Date
    Oct 2007
    Location
    Milwaukee,WI
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    1,097
    Quote Originally Posted by ACFIXR View Post
    Square duct has less resistance to airflow, is cheaper to make, and more economical to install.
    I strongly disagree with everything said here...lol.


    IMO...
    Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.
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  11. #11
    Join Date
    Jul 2009
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    In a mechanical room....
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    Quote Originally Posted by Lash View Post
    I strongly disagree with everything said here...lol.


    IMO...
    Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.
    You got that friggen right!
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  12. #12
    Join Date
    Feb 2004
    Location
    SW Florida
    Posts
    1,264
    Quote Originally Posted by Lash View Post
    I strongly disagree with everything said here...lol.


    IMO...
    Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.
    Our shop can do spiral faster than any cheeser shop

    Also take into account the aspect ratio which is ideally less than 3:1 or 24 x 8, w/h=A.R.

  13. #13
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
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    4,509

    Talking

    Quote Originally Posted by Lash View Post
    I strongly disagree with everything said here...lol.


    IMO...
    Spiral is by far easier to install than sqaure as well as having less resistance to airflow when using full radius elbows. It can also be installed at least 2x faster. And with the use of gasketed fittings, it will also seal tighter than most square duct. Our shop can whip out the spiral like you wouldn't believe. Square duct is used because of the endless possiblities of changing dimensions while maintaining a required area, especially with space limitations. Round is somewhat limited in that area.
    I agree with you on the spiral.........also have found that a round duct can waste more space than a square duct but that the square duct can carry a higher volume or the same air at a lower velocity within the same dimensions. For example a 14" diameter duct verses a 14" square duct.

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    "keeping condensing pressures low and evaporator pressures high"
    "Some customers are more interested in comfort than energy savings"
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