Height of chimney

[Fudugazi]

I am building a 36 inch dome This will be outside Is there an optimal height for the chimney stack The lower profile the better for my site. Any thoughts ?

[james]

In general, pizza ovens draw very well, so the pull of the chimney isn't a huge issue. For our Casa precast ovens, we recommend a 6" system for the 31" and 35" oven and 8" for 39" and 43" ovens. If you are going to use a UL103HT chimney system (double wall steel), the top of the chimney should be 24" above the top of the enclosure -- that is what Simpson Duravent specifies in their UL-approved installation manual. In terms of height, a 36" pipe, attached to the top of an oven vent will typically draw well, and rise above the top of the enclosure to the correct height.

If anyone is interested, Forno Bravo is a Simpson dealer, and we can provide the chimney set -- an anchor place, chimney section and cap/spark arrestor. You can also download the UL103HT installation manual (and UL spec) from our web site.

James

[Jim Bob]

James,
I know its been a while since you posted this info about Chimney height, but I am about to install a terracotta pipe chimney which is 6" inside diameter x 24" long plus the cap. My round oven is 36" inside diameter with a 19" ceiling height inside. Will that cause me some problems? The pipe will be fully bricked in. Also even though your FB specs call for 6" pipe, many of the posts recommend 8" instead even for the 36" oven.
Any thoughts?
Jim Bob

[brokencookie]

If you search the forum for Chimney flow rate you will find a calculator for the draw of the chimney. Using your numbers ( 6 inch pipe) I get a draw of 358. We only have a little data but the smallest reported sucessful draw rate is 645. If you increase your pipe to 8 in you will get a draw of 648 which we are sure will work. The 6 inch may work but its a little hard to tell since we have such limited data.
A few people have mentioned the transistion being important to the draw of the oven. However, now matter your transistion, if your chimney sucks like a vacuum cleaner on steriods, smoke is going to exit via the chimney.
Maybe we can get a few more people to tell us the size, shape and height of thier chimineys with an opinion about draw to refine the minimum flow rate. Here is a link to the calculator.


http://www.fornobravo.com/forum/f28/...ator-3905.html (chimney flow rate calculator)

[Jim Bob]

Thanks very much for the help. You have helped me avoid the mistake of too small a chimney. Will change to 8" pipe. Of course in order to use your very simple calculator I will have to dig up my metric conversion kit again. The final resulting number is just that a number, however, you have given us the minimum accepted one and that will be fine with me. I don't want to know too much or someone will start asking me what it means!!!
THanks,
Jim Bob

[Jim Bob]

After Extensive inquiries into various available flue liners it is now obvious that we are NOT talking about 8" x 8" inside diameter for the flue. That is the outside diameter and it is 6" x 6" inside diameter. Four major brick companies in Memphis say that what they list as an 8 x 8 liner is based loosely on the outside diameter and the inside is 6 x 6. The next size available up is 13" x 13" outside diameter, which is too big. So, I may already have the appropriate size after all.
Jim Bob

[nissanneill]

Hi Jim Bob,
Why not use an 8" stainless steel flue instead of a terracotta?
Much cheaper, easy to get, work well, need I elaborate further?
I have a 40" Pompeii and my 8" flue which is 3 metre tall (to get any smoke on light up above the neighbours), has a draw value from an oven temp of 50˚C of 514.1 and when it is 500˚C, that value goes up to 1329.3.
Don't ask me what that means but I know it works an absolute treat and no smoke at all escapes from the front arch. A smaller chimney will not cope with the load put upon it and have start up smoke coming out the front. (The forum is trying to find out the minimum value when this does not occur).

Neill

[Jim Bob]

Neill,
Thanks for feedback. I went shopping again yesterday and found a larger terra cotta flue liner. It is an 8.5" x 8.5" x 24" long. The 8.5" is measured diagonally and is the inside diameter. No wonder I couldn't locate the larger one, i had no idea they were talking about diagonal measurements. Hopefully this will do the trick. I was also lucky enough to locate a nice "bird cage" type cap for the liner that fits at a local fireplace store. So it will be installed tomorrow.
I just wish everyone would go back to Fahrenheit and inches instead of Centigrade and metric. I am too old to change now!! Have to keep looking up the conversion chart! Unless my numbers are way off, a 3 meter chimney is almost 10' tall!!! Where did I go wrong? Mine is only
24" tall.
Jim Bob