How to determine correct chimney height

[Breven]

I remember seeing a thread or two that mentioned a chart or something to determine the correct chimney height. I'm building a 36" Pompeii. I have a 6" base plate installed now. I plan to enclose with a house. I was thinking around 3 feet, but I want to make sure the oven draws well, I want to avoid smoke out of the front.

Does anyone know the formula?

Thanks-

[krosskraft]

Re: How to determine correct chimney height

From what I remember the chimney needs to be 2 ft above any structure within 10 feet. My oven is about 6 feet from the house, so I added an extender to make my chimney 2 feet above the roof height that is 10 ft from it. It draws very well. The chimney company that provides the chimneys for Forno Bravo can help you with that info.

[dbhansen]

Re: How to determine correct chimney height

Reviving this thread...

The FB plans call for a chimney about 3-4 times the door height, but the parts list in those plans calls for a 2-3' chimney.

My 42" oven (with no other structures nearby) has a door height of 12", which equates to 3-4' using the door-height formula.

This is a moderately windy area. So can I get away with a 3' chimney, @ 8" diameter? Or would 4' definitely be better?

Daren

[Breven]

Re: How to determine correct chimney height

With my chimney, I went with a 6" diameter, 3' tall. I'm getting a pretty good draw- only a little bit of smoke coming out of the front when I first start the fire, then 99% is going right up the chimney. It seems to draw better with less wind. Also, I lowered my outer arch about an inch, someone made that suggestion here somewhere. It really has made a difference. I've wached smoke hit that lip, curl under and get sucked up the chimney.

You will also notice, my chimney is only a few feet from my house. I didn't want an 8 ft. chimney, because it would look so fricken strange. So, I'm just breaking the rules here. So far I haven't seen a single spark make it out of the chimney, so I'm not worried about being too close to the house. Is it to code? Nope...but that's o.k. I've left the chimney in a position that I can unlock it and ad an 8ft if I ever need to.

[dbhansen]

Re: How to determine correct chimney height

Thanks, I think I will start with 3' and see how it draws. And lowering the arch ... I'll have to consider that this weekend when I build my outer arch.

[dbhansen]

Re: How to determine correct chimney height

I lowered my outer arch about an inch

Breven, did you lower only the very outer decorative brick arch, or did you also lower the outer firebrick arch that supports the chimney?

[Breven]

Re: How to determine correct chimney height

Just the very outer arch. The firebrick arches are even. I added an additional decorative arch (the brown bricks) just for esthetics, so it would stick out in front of the enclosure. The enclosure walls were even with the outside firebrick arch. The idea is that any smoke that makes it past the chimney opening will hit that lip a little, holds up just long enough for the draw to suck it in. Seems to work.

I read a thread somewhere on here about tips and tricks to help keep smoke from coming out of the front. I didn't make a very big flue opening, so I figured I had better do what I can to help before that becomes a problem.

[brokencookie]

Re: How to determine correct chimney height

You will find a good discussion and a chimney draw calculator here.

http://www.fornobravo.com/forum/28/c...or-3905-3.html

This will allow you to see the effect of flue diameter and chimney height on the draw.