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Flue area to door area question? Confused again - Forno Bravo Forum: The Wood-Fired Oven Community

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Flue area to door area question? Confused again

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  • Flue area to door area question? Confused again

    My doorway is 22" wide and 10 1/2" high. The door is a perfect semicircle so the door area is more or less 175" square so the flu would need to be 17 1/2" square area therefore the flue would have to be under 5" in diameter according to the info I have found on this forum.....(Ideal Flue is 10%area of the door area). This seems small for a 42" oven...any ideas? Thanks

  • #2
    Re: Flue area to door area question? Confused again

    I don't know where abouts in this forum you sourced these figures, but I would not have less than an 8" diameter stainless chimney. My oven is a 40" with an 8" diam and 12' long chimney which draws like a dream.
    Go with your heart rather than a well intended formula but the FB ovens recommend an 8" one also I believe.

    Neill
    Prevention is better than cure, - do it right the first time!

    The more I learn, the more I realise how little I know


    Neillís Pompeiii #1
    http://www.fornobravo.com/forum/f8/n...-1-a-2005.html
    Neillís kitchen underway
    http://www.fornobravo.com/forum/f35/...rway-4591.html

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    • #3
      Re: Flue area to door area question? Confused again

      Originally posted by nissanneill View Post
      I don't know where abouts in this forum you sourced these figures, but I would not have less than an 8" diameter stainless chimney. My oven is a 40" with an 8" diam and 12' long chimney which draws like a dream.
      Go with your heart rather than a well intended formula but the FB ovens recommend an 8" one also I believe.

      Neill
      I found it here, http://www.fornobravo.com/forum/9/ch...tml#post107039

      I see the FB flues are 8" but if you inspect the plans the flue entrance is only 6" so the extra 2" and area seems redundant. Form my research it seems most commercial italian ovens have a 6" flue
      Check the plans on page 9 and 10 of this pdf http://www.fornobravo.com/PDF/Casa2G_datasheet.pdf and see what you think?

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      • #4
        Re: Flue area to door area question? Confused again

        Those entry/flue proportions are rules of thumb for masonry fireplaces. You needn't be concerned about those unless you are trying to push through an indoor oven through masonry fireplace code compliance.

        Pompeii recomendations are for a 6" round flue for a 36, and an eight inch for a 42. The smaller flue will work, but not keep smoke pouring out the entry on startup. I have a 36 with an 8" squarish flue tile, and there is no problem with too much air flow.
        My geodesic oven project: part 1, part 2

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        • #5
          Re: Flue area to door area question? Confused again

          They are minimum numbers and apply to round flues in fireplaces. For ovens the formula is generally too small.

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          • #6
            Re: Flue area to door area question? Confused again

            I found this on an italian Oven building web site
            Diametro del forno diametro minimo canna fumaria in cm
            da 60 a 80 ----cm 20
            da 80 a 120--- cm 25
            da 120 cm in--- su 30

            Costruzione e uso del forno a legna

            Translated... Translation result for Costruzione e uso del forno a legna

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            • #7
              Re: Flue area to door area question? Confused again

              I have a 190 cm oven with an 8" ss flue and it works great.
              Our Facebook Page:http://www.facebook.com/pages/Stoneh...60738907277443

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              • #8
                Re: Flue area to door area question? Confused again

                Flue size. The US underwriters Laboratories state that it is best to use a flue as large as you need and no larger;
                So if you were burning 12 lbs/hour of wood you would be generating 97,000 btu's and therefore need a 6" Flue (My 41" oven would burn less than this)
                16.5 lbs/hr=7" according to The US underwriters Laboratories.
                21.6 lbs/hr=8"
                27.3 lbs/hr=9" and so on

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