#1  
Old 08-12-2009, 11:18 AM
Serf
 
Join Date: Sep 2008
Location: Wisconsin
Posts: 6
Default How big a vent for a 42" oven.

Hello from Madison Wisconsin. My hopes for the Badgers football season are not very high so I've decided to focus on building an oven instead. I'm building a 42" Tuscan style dome oven (21" high), following the Forno Bravo plans (version 1.2) pretty close. The vermiculite insulating layer is poured and drying and now I need to lay out the oven, opening, etc. The insulating layer is 75 deep by 69 wide.

For the opening I was planning on following the plans: so about 20" wide by 12" tall, square because we will make it from angle iron and brick of course.

My question is about the vent size I should shoot for. I'm going to have a local shop fabricate a vent from SS and then use a commercial clay flue. The flue sizes are, according to my mason, 9 x 12, 12 x 12, 8 x 8. Those are OD measurements. I've got a call in to see about other sizes. Take away for the thickness of the clay and you have, I suppose a 7x10, 10x10, etc inside diameter for the flue.

If the opening is 20", I imagine the vent will be about that wide, or 20".

But what depth do I need to shoot for??? The pictures of steel vents in the plans are hard to follow, and I don't see any discussion of minimum sq inches of vent opening to get a good draw and keep the smoke from billowing out the opening arch. It seems logical that at some point it can get too big, but it also seems like more vent opening and a bigger flue size will lead to better draw and a better fire. My yard is sort of sheltered from the wind too, I might add.

Anybody have an opinion, I'd love to hear it. I'm getting ready to outline the footprint so I need to set that vent depth pretty soon.

P.S. Is it wise to "slope" the brick arch upward to the vent too??

Thanks!!!
Reply With Quote
  #2  
Old 08-13-2009, 07:23 PM
Journeyman
 
Join Date: Jun 2009
Location: minnesota, usa
Posts: 472
Default Re: How big a vent for a 42" oven.

my understanding of vent design is basically the bigger the better, or the more volume at the start, the better, but I'm sure I'm oversimplifying. I my arch is 10-12"h x 18"w. My vent starts out just under 18 w. and tapers up to meet the 6"dia. anchor plate for my chimney over what amounts to about three courses of brick, or roughly 8". It draws beautifully with one 3' section of chimney.
If your arch width is 20"id, then yea, I guess I'd spec that assuming it's going to have a flange to attach it to the brick. Based on my experience, I think whatever taper you put on it will be just fine, but I'm certain I read something here about vent volume vs. chimney diameter. If you can't find it, google might work.

Last edited by splatgirl; 08-13-2009 at 07:28 PM.
Reply With Quote
  #3  
Old 08-13-2009, 08:48 PM
dmun's Avatar
Moderator
 
Join Date: Jul 2005
Location: New Jersey USA
Posts: 4,216
Default Re: How big a vent for a 42" oven.

There are rules about flue size in masonry fireplaces, where the flue area is a certain fraction of the fireplace opening. Since we have fairly small openings, we don't need huge flues. The 8 by 8 is what i used, and it draws like a champ, but my chimney is two stories tall which helps a lot. The rule of thumb about your transition is that the bottom should be twice the area of the top.
__________________
My geodesic oven project:
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
,
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #4  
Old 08-14-2009, 11:11 AM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: How big a vent for a 42" oven.

For a 42 inch oven, I suggest about 60 to 80 square inches of vent funneling up to about 30 to 40 square inches of chimney.

One other note. I see your dome is to be 42 inch. I suggest that the dome be elliptical in shape with a height about 85% to 90% of the radius which would be about 90% of 21 =18 3/4 inches in your case.

Another dimension, and this one is critical to a well functioning dome oven, your door height should be 62% of your inside oven height. Or, in your case, 62% of 18 3/4 = 11 5/8 inches.

Last edited by Neil2; 08-14-2009 at 11:20 AM.
Reply With Quote
  #5  
Old 02-10-2011, 01:37 PM
Apprentice
 
Join Date: Jul 2006
Location: Dorset, United Kingdom
Posts: 149
Default Re: How big a vent for a 42" oven.

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
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Why Italian Wood-Fired Ovens are Round james Newbie Forum 50 04-01-2014 10:14 PM
Pizza in a Bread Oven james Newbie Forum 17 04-24-2012 08:13 PM
Tuscan and Naples designs james Pompeii Oven Construction 5 09-11-2011 05:53 PM
Oven vent....will it work? rwiggim Pompeii Oven Construction 14 11-24-2007 07:53 AM
Oven & Vent Opening Size Hendo Pompeii Oven Construction 1 02-01-2007 02:47 AM


All times are GMT -7. The time now is 10:21 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC