Rear Chiminey

[lwood]

I don't see anything on "rear chimneys". I want my oven to look like the one in the Frorno Bravo site (attached pic). It appears to have the chimney in the rear. How do I achieve that look?

[Neil2]

Re: Rear Chiminey

No, you don't want that.

Think of it as a "vent" not as a conventional chimney. It is situated outside of the oven over the entryway and its function is to divert hot gasses away from your face as you operate the oven.

The thermodynamics of a pompeii oven are such that the hot gasses from the fire, fed by air entering the bottom of the door, rise and exchange heat with the bricks before cooling and exiting the top part of the door. (This is why the door height to oven height ration of 0.63 is important.)

If you install an internal chimney, you will create an air flow that will quite negatively affect your oven efficiency.

[lwood]

Re: Rear Chiminey

Ok, so how do I achieve the look in the photo?

[dmun]

Re: Rear Chiminey

That's a modular oven (i think the Forno Bravo Artigiano) uninstalled, uninsulated, with a light bulb in it for a photo op. All successful wood fired ovens have their vents in the front, over the entry.

[lwood]

Re: Rear Chiminey

Ok, I was afraid that was the answer. No problem, how about this one.

[Neil2]

Re: Rear Chiminey

"No problem, how about this one."

That is a style that also has a vent in the front. The flue portion is then curved over the outside then vertical at the top of the dome. If you look closely at the top front, you can see a "bulge" where the flue goes.

[lwood]

Re: Rear Chiminey

Gotcha, thanks.

[texassourdough]

Re: Rear Chiminey

Diverting the chimney back over the oven can definitely be done but it is important to do it right so that you have enough flow area to draw well - the curves (and potentially worse) don't help the chimney draft! Be sure to oversize the flue!

There is another issue with internal chimneys that is worth mentioning - it would greatly limit your ability to bake for the hot air would simply go up the chimney (and let cold air down!)

Jay

[christo]

Re: Rear Chiminey

There are some posts on squirell tale ovens that route the smoke from the front to the back. Also google will show you some others.

http://www.fornobravo.com/forum/f9/squirrely-4416.html

MHA News - 2006 Meeting - Backyard Oven with Peter Moore

Christo

[edf74]

Re: Rear Chiminey

I am in the process of building pizza oven now and would like to put a fireplace next to it. Does anyone think it is possible to join the two flues and go up in between them?

[mhannawa]

Re: Rear Chiminey

i just finished my first wfo and i placed my chimney in the rear. having realized that that was a mistake from the test run, i quickly adapted with an adjacent fan that ties into the lower portion of the chimney duct. i used a 12 volt computer fan that draws air from the ducting i created reduced down to 1 1/2 inch outlet. i installed it into the hole i cut out of the chimney duct. i pitched it about 30 degrees upward to create an upward draft. i run it off of my car battery jump box, and it can run for up to 6 hours. it cost me about $30 in materiel, and i have to say, it worked far better than i expected. 80% of the smoke is now channeled through the chimney, and the fire rages on start-up due to the forced suction of oxygen from the door opening . yes, it's unorthodox, but it works like a charm. the oven reaches cooking temperature in about 30 to 40 minutes. you are probably still going to bash me for this advise LOL.

[Breven]

Re: Rear Chiminey

No bashing from me....you do what you gotta do to make it work! However (here comes some mild bashing) I personally think that one of the coolest part of building a WFO oven is how effecient you can make it using basic materials. I mean, this is a 2,000 year old design that works perfectly without electricity and fans. That is, if you build it right! of course...I've never had my oven up to temp in 30 minutes- which would be nice.

[ThisOldGarageNJ]

Re: Rear Chiminey

Ed

19b

I am in the process of building pizza oven now and would like to put a fireplace next to it. Does anyone think it is possible to join the two flues and go up in between them?

Flues may slope to join with other flues so as to discharge through a common flue, or to achieve the desired location of the chimney. The maximum allowable slope is 30 deg from vertical. When combining flues the main discharge flue should be sized for the maximum combined flow from the smaller flues. Combining flues of dissimilar systems or fuels. i.e., appliances and fireplaces, is not allowed by many building codes. Separate flues may be incorporated into one chimney so long as minimum wall thickness requirements are met and a full wythe of brick is laid between them and bonded to the chimney walls.

Check the link posted above (19B) I think that should answer all your questions....
Mark