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gtofani 10-17-2011 10:35 AM

secondary chimney vent?
 
I have noticed the black discoloring left form the smoke on the decorative part of almost every oven.
Has anyone designed a chimney that eliminates this problem?
I was thinking of placing a thinner secondary transition into the chimney closer to my decorative arch.
Maybe just use smaller slices of brick for the top inner vent arch right before it reaches the decorative arch or entry way.
This should give the black smoke another chance to move up into the chimney instead of exiting through the front.
Or at least cut down on the amount that comes out the front.

SCChris 10-17-2011 11:17 AM

Re: secondary chimney vent?
 
The smoke could be avoided by using a baffle outside of the chimney to lower the entry height a couple of inches and still allow wood to be added. This sort of accessory might be just a little stainless sheet metal that extends up into the smoke collection area, down a couple of inches lower than the oven entry height and spanning the full width of the entry in this area, this all supported by some sort of side legs. So for my oven that has a 13.5 inch exit height for the actual oven and a width in the area described of about 24 inches, I’d start with a removable baffle that allows 12 inches of vertical for putting wood into the oven.

Doing this could also help to create a faster flow of incoming, fresh air. Once the fire is rolling and the chimney is warm very little smoke comes out of the entry anyway, but until then smoke can sneak out the front.

Can you provide an illustration of your idea.


Thanks

Chris

PS Like a fireplace, if you start the oven slow, and allow for a bit of warming, very little smoke will make its way forward. Eliminating smoke out the front can be done, but it might be more trouble than it's worth..

gtofani 10-17-2011 11:38 AM

Re: secondary chimney vent?
 
I like the stainless steel baffle idea until the fire gets going hotter.
I thought about a permanet baffle by dropping the outter arch a little but then I would not be able to get my door in and out.
Hope this link works.

Snapfish: Share Photo:Registration

the black represents the chimney inside, the outter arch prior to my outside finish look is where I wanted to cut the arch brick thinner to create more area for the smoke to go up instead of out.
Maybe I can incorporate a stainless baffle that slides up into the arch area that I can pull down when needed.

brickie in oz 10-17-2011 12:18 PM

Re: secondary chimney vent?
 
The only reason the fronts get sooty is because the flue isnt big enough, or the flue gather isnt built correctly, smoke always finds the easiest way out.

SCChris 10-17-2011 12:49 PM

Re: secondary chimney vent?
 
Brickie,

I agree with you, smoke always finds the easiest way out, but it needs to be said that as the chimney heats, the ability to pull the smoke out of the entry increases.

An analogy would be sink with and without an attached drain pipe.. The added mass of the water flowing out the drain pipe helps to pull the water out of the sink. A siphon is another example, water won’t flow above the water supply, but it can be pulled higher, with a siphon, as long as the end of the hose is lower than the source supply.

Once the chimney is hot, the higher the chimney, the better the draw all things being equal.. Many of the problems with smoke escaping the front of the entry relate directly to not having enough area to service the quantity of smoke for the given chimney height. I’m not advocating a 30 foot chimney on a 42 inch oven, I’m just saying, your right “Smoke always finds the easiest way out”

gtofani,
Time to time I have to remind myself.
"Keep it simple stupid"
"Don't be penny wise and pound foolish"
"Do it right" and
"If it's important don't compromise"

Chris

PS.
One more thing; "She is almost always right and she knows it and will remind me of it"
Best to all..

david s 10-17-2011 01:55 PM

Re: secondary chimney vent?
 
It is the volume of the flue that creates the draw. You can increase the height or the cross sectional area, or both. Using the top down method also eliminates smoke at start up. I have a mosaic decorative arch (glossy tiles) occasionally I give it a rub with damp newspaper- no more smoke staining.

Faith In Virginia 10-17-2011 02:42 PM

Re: secondary chimney vent?
 
My chimney works great for the most part. Sometimes as the fire just starts to get big and just the right gust of wind feeds the oven I get smoke out the door. I think if you don't like that look you can always tile the opening so that if it does get dirty it will easily clean(like what David S said). personally I don't mind the markings I think it adds charm to my oven

brickie in oz 10-17-2011 02:49 PM

Re: secondary chimney vent?
 
Quote:

Originally Posted by Faith In Virginia (Post 122071)
My chimney works great for the most part. Sometimes as the fire just starts to get big and just the right gust of wind feeds the oven I get smoke out the door.

Have you tried a blast door?

GianniFocaccia 10-17-2011 02:55 PM

Re: secondary chimney vent?
 
Quote:

You can increase the height or the cross sectional area, or both
I am currently designing my flue and in particular, the size and shape of the flue gather, or vent. I understand that the longer a given flue is the higher the pressure and draw it will provide. Is it incorrect to assume a shorter but larger diameter flue would not provide the same amout of pressure that the longer/narrower flue could?

Faith In Virginia 10-17-2011 03:03 PM

Re: secondary chimney vent?
 
No Al, I have not tried a blast door what are the benefits?


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