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-   Design Styles, Chimneys and Finish (http://www.fornobravo.com/forum/f9/)
-   -   Poll - Chimney/flue diameter (http://www.fornobravo.com/forum/f9/poll-chimney-flue-diameter-1576.html)

jengineer 02-19-2007 04:36 PM

Poll - Chimney/flue diameter
 
reading the material on the FB Forum and web site one gets the notion that on the minimum the diameter of the chimney for a 42 inch oven should be no smaller than 8 inches, 50 square inches. I am searching for the largest cross sectional of the chimney that works.

Has anyone used a larger dimension?
How well does it draw?

CanuckJim - same question jsut modify your answer as appropriate.

Still herding those ants

dmun 02-19-2007 08:48 PM

Re: Poll - Chimney/flue diameter
 
36" diameter, 8" square refractory flue tile, most likely 12-14 feet high when finished, draw to be determined.

Chris 02-19-2007 10:11 PM

Re: Poll - Chimney/flue diameter
 
8 inch I.D. square clay tile. 42" oven. Expect to use 4 feet of flue. Draft TBD.

The wooden box represents the location of the flue tile.
http://fornofumoso.files.wordpress.c...rch-mockup.jpg

Xabia Jim 02-20-2007 12:05 AM

Re: Poll - Chimney/flue diameter
 
39 inch oven, 7.7 inch diameter chimney.

I want to extend my flue because I believe the more flue you have the better the draw becomes as it heats up. I'm also fighting nearby walls. As I recall some codes for house chimneys wanted them to be above the roofline....

carioca 02-20-2007 02:35 AM

Re: Poll - Chimney/flue diameter
 
Muy buenas tardes, XabiaJim!

Building a 39in (1m inner diameter) dome on a hearth 90 cm above ground level.

I've checked with my local council what provisions they have for barbeques (this is an Australian national emblem for the backyard) because I didn't want to try getting approval for a pizza oven.

Turns out you need NO building permit or whatever for a barbeque, provided it is no less than 3 m from the boundary line and is no higher than 1.8 m.

That limits my flue to 50 cm - I guess that would still be o.k.? If not, I'd have to emply the sliding extension type of flue that I've seen mentioned on the Forno Bravo forum...

Salud y pesetas - y putas para gastarlas!

Carioca

CanuckJim 02-20-2007 07:25 AM

Re: Poll - Chimney/flue diameter
 
JE,

It does seem that 8" square flue tile is the standard, not only for pizza ovens and bread ovens, but also for indoor fireplaces. Having said that, however, I used 7" round tile on my 3' x 4' bread oven and it draws exceptionally well, winter and summer. As for height stipulations, most building codes do specify that the chimney must extend above any roofline within 10' or so by as much as 3'. Depends on where you are. But, this is for fire hazard reasons, not draw. The chimney on my bread oven clears the peak by about 18". There is a pic of it in the photo gallery. There are many theories and, I believe, some formulas for the height and diameter of the chimney in relation to the size of the firebox, but these are mainly written for fireplaces and wood stoves, not ovens. Count Rumford of Revolutionary War fame is just such a mathematician.

Of course, as the flue gasses rise, they begin to cool. In my experience, an exceptionally long flue contributes to creosote deposits, but this is based on fireplaces and woodstoves. Seems to me, at the heat our ovens burn, that the length of the flue is not as critical as in these other applications.

I get zero smoke out the mouth of my oven, UNLESS the wind is blowing horizontally from the south, directly into the mouth itself. In these conditions, I shouldn't be outside anyway, because a howler is on its way. Essentially, I designed the total height of the chimney more for aesthetic than mathematical reasons, and it works just fine. The total flue is quite short, and this contributes to a clean interior.

Jim

jwnorris 02-20-2007 10:17 AM

Re: Poll - Chimney/flue diameter
 
My Casa110 [43" ID] has a 8" DuraTech SS dual-walled flue extending 6' above the oven.

J W
:cool:


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