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  1. #1

    how big should the supply plenum box be?

    75K high-efficiency upflow unit. No A/C. 16.5x20" opening. I need ~300 sq. in worth of supply.

    Square ducts, so it can come mostly off the top if the sides angle outward into a 22x20 top. Maybe one 3.5x10 in the side.

    I'm thinking 20" high for the box, plus head space for two 7x20 elbows. Can it go shorter? Does it need to go taller?


  2. #2
    Join Date
    Jan 2004
    Lancaster PA
    So you decided to DIY.
    Contractor locator map


    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Jun 2004
    Howell, Michigan
    This is not a DIY help site. We can't help you install your furnace.

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