Connecting “Flex Duct†to a heater

Discussion in 'HVAC Heating & Cooling' started by lahabra, Mar 12, 2008.

  1. lahabra

    lahabra New Member

    Dec 21, 2007
    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. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    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.
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  4. Nubbin

    Nubbin New Member

    Mar 30, 2008

    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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