Forno Bravo Forum: The Wood-Fired Oven Community

Forno Bravo Forum: The Wood-Fired Oven Community (http://www.fornobravo.com/forum/)
-   Design Styles, Chimneys and Finish (http://www.fornobravo.com/forum/f9/)
-   -   Chimney Not Drawing Enough (http://www.fornobravo.com/forum/f9/chimney-not-drawing-enough-7295.html)

Harrison 07-22-2009 02:51 AM

Chimney Not Drawing Enough
 
2 Attachment(s)
hi guys,

just starting to use my barrel vault oven. I have gone through the curing fires with no real issues (some small cracks). my main concern is my chimney doesn't seem to draw enough of the smoke as it spills out the front arch.

I have made my chimney just outside of the door/opening. Im thinking of cutting out a small hole (size of half a brick) at the front end of the dome just above the door and feeding it to the chimney. Im hoping this will also help my fire to breathe as it appears to be choked by the excess smoke in the dome.
If i blast the fire with a hairdryer, it burns well, but soon after i move the dryer away it dies down again..

i will try and post a few pics of my oven. i will appreciate any feedback ond or advice on my situation.

EDIT: i also have a 3ft galvanized chimney flue which is detachable and is not in the pic

Rastys 07-22-2009 03:23 AM

Re: Chimney Not Drawing Enough
 
Harrison
from your picture, it is obvious that your chimney void and size is way too small for your oven size.
Look at your opening closeup and you will see that the top 1/3 of the oven opening has smoke stain on it and all that smoke is expected to go up that little chimney hole.
I have a 40" Pompeii with a a stainless void the full width of the door 24" x 15" and funnels 18" up to an 8" round flue. No smoke exits my front arch unless I use the petrol leaf blower to change it from an oven to a bast furnace.
It should be easy to correct by cutting (or using numerous masonary drill holes through the bricks) and making the chimney entrance
hole double the size.
The fact that it is just an open hole and not a funnel shape, you will still get some, all be much less, smoke out of your front arch. I would also then make a plate to reduce the void size to fit your flue diameter but I would ensure that it was at least 8" or preferably larger. The larger your oven, the larger the chimney needs to be.

Rastys

CanuckJim 07-22-2009 03:34 AM

Re: Chimney Not Drawing Enough
 
Harrison,

I have a barrel vault oven as well. The method and size of opening are basically the same as what Rastys used. I get zero smoke out the front, and the chimney draws like a locomotive. Suggest you do a search of the photo gallery for vent and chimney work by members. Rastys is right on in what he recommeds. However, three feet of pipe is not enough;should be above four for the best draw. Don't go cutting holes in anything; just make the vent area larger and taper it upward to where the flue begins.

Jim

dmun 07-22-2009 07:08 AM

Re: Chimney Not Drawing Enough
 
Quote:

Im thinking of cutting out a small hole (size of half a brick) at the front end of the dome just above the door and feeding it to the chimney.
This is a really bad idea. You wouldn't have built a barrel vault oven if you didn't want to do retained heat cooking, and this vent will suck all the heat out of your oven.

Dutchoven 07-22-2009 04:42 PM

Re: Chimney Not Drawing Enough
 
Absolutely don't go cutting anything. When we built the barrel vault in our back yard I made a similar mistake. The vent opening to our chimney there is about 5 inches deep by nine inches wide so it appears to be about the same area as yours. Other than that is appears that the oven is a similar shape. We get some smoke puffing out the front but mostly in the beginning of the fire. I think you could get by with increasing the height of the chimney. I do think that the detatchable thing could be creating a problem as well in the sense that without a really good seal your flue could be acting like a mixing valve sucking fresh air in at the crack and thus slowing down the flue gases on the way up.
All the best!
Dutch

Harrison 07-22-2009 11:59 PM

Re: Chimney Not Drawing Enough
 
thanks guys.. im going to try the longer flue first.. if thats a no go then im bringing out the angle grinder and widening the chimney to the width of the oven door..

im hoping this chimney fix will also take care of the smoke buildup inside.. im already in trouble for using the mrs' hair dryer to blast the fire..

karl 07-23-2009 03:30 AM

Re: Chimney Not Drawing Enough
 
Remember that even with a higher (longer) chimney (which should help a lot) it needs to heat up before it works properly. I suggest that you prime your flue gas stack by starting a small fire just below the flue gas exit before you start your main fire in the oven.

Regards from Karl

BurntFingers 07-23-2009 05:56 AM

Re: Chimney Not Drawing Enough
 
Keep it hot and make it 3X to 4X higher then it will draw like a factory.


All times are GMT -7. The time now is 04:43 PM.

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