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Draft Hood Question..

Foreman
Foreman Member Posts: 30
in THE MAIN WALL
Interesting....seems they would disable the burner if draft is obstructed. I know mine has a high temp snap switch mounted just under the hood, where hot flue gas would expel if flue or chimney was obstruced. When I pull one wire of it (simulating blocked draft), it shuts down the burner, therefore it would not continue any heating cycle until you reset the snap switch.

Comments

  • Foreman
    Foreman Member Posts: 30



    I was wondering while cleaning my boiler, is the draft hood to reduce flue temp, or so you dont pull too much draft off the burner area?

    Seems to me it would be to reduce flue temp, since they recommend a minimum distance from the boiler jacket.

    Any input?
  • Mark Hunt
    Mark Hunt Member Posts: 4,908
    The drafthood


    or "draft diverter" serves one purpose. To disconnect the vented appliance from the chimney. It will allow the appliance to continue to vent into the structure if the chimney is plugged.

    This is right from GAMA.

    Mark H



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  • Mark Hunt
    Mark Hunt Member Posts: 4,908
    Some


    appliances are equipped with spill switches like you mention, but some are not. Look at water heaters.

    Also, the spill switch needs to be in the stream of the flue gas in order to detect the back-up. I have seen instances where the flue gas was spilling out of the draft diverter on the opposite side of the spill switch and the switch never opened.

    The draft diverter was designed to prevent pilot light blow outs caused by down draft and to allow the appliance to vent into the structure should the chimney become plugged. Spill switches were added as a feel good measure so that manufacturers didn't have to drastically alterate their designs.

    Why no draft diverters on oil equipment? Oil appliances have barometric dampers that you can adjust while atmospheric gas applainces have draft diverters which are NOT adjustable. Excess air and dilution air are fixed with draft diverters.

    Then again, I can count on one hand the number of plumbing and heating contractors that actually test for those things in my area.

    Mark H



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