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duct transition from air handler to main trunk, any suggestions?

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skyking1
skyking1 Member Posts: 142
in THE MAIN WALL

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  • skyking1
    skyking1 Member Posts: 142

    I have built the ductwork up to this last step, connecting the air handler to the 10x24 main duct that is ~17" above it.

    The top of the blower is this:

    image.png

    do I get a 10x14 bent up and then hard attach it to the duct above, and use a hardcast canvas joint at the top of the blower?

    Or should I transition from 10x14 to a larger size in that ~14" above the canvas joint?

  • Jamie Hall
    Jamie Hall Member Posts: 27,352

    Not a hot air guy — but an airplane guy, add my take would be either will work, but make it so that the bends are as gentle — large radius — as possible, and the dimension change as smooth as possible.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    skyking1
  • Kaos
    Kaos Member Posts: 863

    Generally around me the plenum is hard connected to the air handler. Since you have a compressor in there, that will be loud, so a soft conneciton to the furnace to plenum is a good idea.

    The plenum should be the size of the air handler, not the blower outlet. You have to think of it as a large space where flow velocity is low that all trunks feed from. This way the trunk takeoffs can be from any side without adding restriction.

    Trunks should be connected with an offset collar the plenum for least flow resistance.

    I generally install the largest standard furnace filter box you can fit. Last longer, less resistance, less maintaince. If you are in a fire area, a 5" might be a good idea so you can run a 1" carbon with a 4" filter during fire season.

  • pecmsg
    pecmsg Member Posts: 7,051
    IMG_3161.jpeg
    skyking1
  • skyking1
    skyking1 Member Posts: 142

    another airplane guy here @Jamie Hall but my avatar gave that away.

    What I have is a horizontal 10x24 trunk that is not directly over the air handler. so I can either build a slightly smaller stack duct than the top of the unit, or go through all sorts of angsty bends to reach over to the trunk,

    I think the former solution will be cleaner, flow-wise. I can get a local HVAC shop to make that final play and I just might do that.

    @Kaos this is the modular 4 ton GeoCool and the compressor unit is remoted about 2' away so no compressor vibrations to deal with.

    The stack of modular components was about the same height as the bottom of the trunk so it got de-stacked.

    Thank you all.

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