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Thread: Connecting “Flex Duct” to a heater

  1. #1
    DIY Member lahabra's Avatar
    Join Date
    Dec 2007

    Exclamation Connecting “Flex Duct” to a heater

    I am planning a new heater install, I want to use Flex-Duct for the supply air and for the Return air.

    I am concerned that the hot air could melt or burn the plastic hose if it is too close to the burner.

    1. Can I connect Flex Duct directly to the a heater?

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    I don't think so. There are some metal flexible ducts, but rigid ones probably work better. I do not know what the codes say. The additional turbulance and friction will slow the air down, too, and give any dust a good hiding place to build up.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

    Default duct

    some codes/install instructions require the flex duct to be kept 4 inches away from ANYTHING that reaches 250 degrees F. The outlet of a gas furnace is often limited to 160-180. However, a short plenmum will move the duct(s) further away from the radiant heat of a heater and improve air flow and reduce a chance of causeing hot spots in your heater that would void your warrant.


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