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elbows in flue/chimney - Forno Bravo Forum: The Wood-Fired Oven Community

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elbows in flue/chimney

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  • elbows in flue/chimney

    I would like to have roof hang over oven entrance - cantilevered - it would require the flue/chimney be pushed back to a central position over oven - to allow longer ridge beam. Does using 30 degree elbows significantly hamper draft? Is stainless steel duravent only way to go or alternatives???

  • #2
    Re: elbows in flue/chimney

    I am sure you can use other venting pipe brands like Metal-fab, Metalbestos, etc. as long as they're Class-A Chimney Vents. Simpson-Dura vent is one of the most expensive.

    You can also use galvanized venting pipe. (still Class-A) It has a stainless steel core, but galvanized exterior- cuts the price down.

    30 degree angles are fine.

    Or- I've seen pictures of people doing the whole thing out of brick.

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    • #3
      Re: elbows in flue/chimney

      Duravent systems seem expensive until you consider the labor of a flue-tile-lined masonry chimney. They are also lighter, and easier to support for offset chimneys.

      To your original question: straight line flues do draw better. Consider going through the roof and flashing around the chimney.
      My geodesic oven project: part 1, part 2

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      • #4
        Re: elbows in flue/chimney

        Hello there. Could you tell me how tall can a chimney be?

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        • #5
          Re: elbows in flue/chimney

          Originally posted by eavila View Post
          Hello there. Could you tell me how tall can a chimney be?
          As tall as you want it.
          You need to get it at least 300mm above any roofs etc or 300mm above a point that is within 3.5M.

          The English language was invented by people who couldnt spell.

          My Build.

          Books.

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          • #6
            Re: elbows in flue/chimney

            Pretty tall if you think about flues/chimneys that are attached to 3-story houses.

            Below is a calculator for Natural Draft Air Flow and Velocity that takes into account external and internal temperature differences. I used to have the URL of a site that calculates flue pressure based on it's diameter and length dimensions, but can't find it.

            Air Flow and Velocities due to Natural Draft

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            • #7
              Re: elbows in flue/chimney

              Thank you, that is very clear.

              While I'm at it, I will build a 42" oven. I downloaded the instructions from Forno Bravo, and I'm trying to understand all the aspects of the building process. I will build the oven on the outside of the house while the opening will be inside the kitchen. The wall is 5" thick.

              How long should the vent wall need to be in order to house the chimney on the outside, without making it unconfortable to work the oven from the cooks position on the inside.

              ¿Can an oven have a second opening, for wood feeding, on the outside?, ¿Can the chimney be attached to this second opening?

              Thank you again,

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              • #8
                Re: elbows in flue/chimney

                Study some of the outside builds on this site. Many have entryway depths of 12-14", not including the decorative arch face bricks. You can angle your flue back towards the rear of the dome (30deg max) so that it rises vertically from the center of the dome. I am ignorant of the code regarding enclosing a flue with one side of the enclosure being your house.

                Don't consider a second opening at the back of your oven for chimney, wood-feeding or winking at the wife through the oven inside your house. Ovens work utilizing a proven air-in, exhaust out path through the front of the oven only.

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