Help- Transitioning from duct board trunk to metal

Discussion in 'HVAC Heating & Cooling' started by Europe72dead, Apr 16, 2021.

  1. Europe72dead

    Europe72dead New Member

    Joined:
    Apr 16, 2021
    Location:
    NJ
    Hello,

    I currently have a duct board trunk from my air handler in the attic to a supply plenum in my kitchen which services the entire first floor. The trunk travels through a closet on the second floor.

    I need to relocate the plenum on my first floor which means moving the trunk over a foot in the closet space. I plan to do this by transitioning to an offset in the closet. Some photos below of what I plan to have built. Everything below the metal offset will be metal.

    Question- what is the best way to transition from my duct board trunk to a metal offset? The metal offset will be insulated and drop down through the floor to a new metal plenum.

    Would inserting the metal offset inside the duct board and then using sheet metal screws with big washers work? The washers would insure the screws don’t go through the duct board. I’m even thinking about using toggle bolts to really connect the two pieces.

    Thanks!
     

    Attached Files:

  2. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Looks like the duct board drop is tight in the closest with limited space to get to the back and sides. A canvas connection would help with insulation of the fitting. Fender washers and self tapping screws from the inside out with the sheet metal over the duct board with a inspection plate to get into the duct. Might also have made some 1.5" -2" sheet metal angle for securing fitting to the floor. Aluminum tape and duct sealing mastic.
    https://www.lowes.com/pd/Design-Polymerics-64-fl-oz-Gray-Duct-Sealant/3736193
     
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  4. Europe72dead

    Europe72dead New Member

    Joined:
    Apr 16, 2021
    Location:
    NJ
    Great solution here, cutting a window in the offset and screwing from the inside seems like my best option.

    I was planning on connecting the offset to a 12” long steel duct that would go through the floor and meet up with the new plenum supply box I have built. Is this where you would use the canvas connection instead to give me some wiggle room? I’ve never heard or seen one of these before but looked them up- they seem very useful, and can dampen and vibration noise. I assume duct board does this also which is why I’ve never heard anything.



    thanks again,
     
    Last edited: Apr 19, 2021
  5. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Canvas connection makes fitting the connection easier as not trying to wrestle the whole fitting and if the fitting isn't 100% perfect it will make up the difference
     
    Europe72dead likes this.
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