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  1. #1
    CaLevi Guest

    Question Duct/trunk routing - 45deg angles?

    One of the 2 main trunks in our basement wastes a lot of headroom space. I wanted to know if there are any issues with running 45deg angles in main trunk lines.
    The stairs are built in the middle of the house, so they routed the trunk line way out to clear the stairs to make a straight path, and I'm wondering if I can re-do it so that it runs straight with a 45deg leg in it that would run parallel to the stair well.

    It would look like this :
    ____/-------- ; as best as keyboard characters can 'draw'.

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,046
    Quote Originally Posted by CaLevi View Post
    One of the 2 main trunks in our basement wastes a lot of headroom space. I wanted to know if there are any issues with running 45deg angles in main trunk lines.
    The stairs are built in the middle of the house, so they routed the trunk line way out to clear the stairs to make a straight path, and I'm wondering if I can re-do it so that it runs straight with a 45deg leg in it that would run parallel to the stair well.

    It would look like this :
    ____/-------- ; as best as keyboard characters can 'draw'.
    It really should not matter as long as the dimensions remain the same. It will ad a friction loss but without seeing a layout of what you have it would be hard to be precise. Could you post a picture?

  3. #3
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,802
    As long as the fittings are constructed properly with radiused throats, the losses will be minimal.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  4. #4
    CaLevi Guest
    Here is a picture :
    http://hvac-talk.com/vbb/picture.php...ictureid=15312

    the green arrow is how I wanted to re-route the square ducting.

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,046
    Should not be a problem, as stated make sure your duct fittings are made with radius not squared

  6. #6
    Join Date
    Oct 2010
    Location
    AZ
    Posts
    614
    Also, make sure there are not two angle pieces too close together. There should be a fairly long straight section between the two turns.
    1775 June 26-July 6. (Declaration of the Causes and Necessity for Taking Up Arms) "Our attachment to no nation upon earth should supplant our attachment to liberty." -Thomas Jefferson

  7. #7
    CaLevi Guest
    The main trunks are square ducts, with the branches to the vents being round ducts. I'm not clear on 'radiused throats'/'duct fittings are made with radius not squared'. Can I not make these bends using square transition/angle pieces (assuming they exist)? or is the argument that I need to throw out the square existing and replace the main trunk with round ducts? I was hoping to re-use the square ducting and simply re-route it.

  8. #8
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,802
    No, the main rectangular trunk lines are fine. The 45* angles you propose should be radiused (rounded) both the outside curve as well as the inside curve (throat) to facilitate better air flow and less turbulance.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


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