Chimney problem?

[rjohnson]

hI, I posted a thread about a week ago with concern about too much smoke coming out the front of the oven I was unable, due to other commitments, to get some pictures and post them so am starting again. Oven is 36" diam with about 19" ht at inside dome, door is 12H x 19W. Entrance is about 3/4" higher and wider and 2.5 bricks deep [so about 15"] . The pictures show it with 1 2" layer of ceramic blanket and the rest will be applied when the brick work gets done. It is holding heat very well. oh, the chimney is 6 x 36 and the vent is 7 x 8

[jeeppiper]

Re: Chimney problem?

I would say your "Vent" is too small...ideally, I think the vent should span the width of your opening and have as much volume as practical. Chimneys like to breath, and will "Draw" in a cyclic manner particularly when there is wind present. So your vent area needs to be able to hold the smoke, until the chimney can draw it out on its next breath. I have a very large vent area (I call a "settling chamber") and have very little smoke come out the front.

Just my thoughts...

[david s]

Re: Chimney problem?

New ovens are notorious for being smoky so you may try just firing some more before doing anything drastic. Also, until the flue has heated up a bit it doesn't draw particularly well so start the fire really small to begin with. Some folk start the fire under the flue to warm it then push it back into the oven proper. Jeep piper's suggestion is a good one, but requires a partial rebuild that you may not need.

[rjohnson]

Re: Chimney problem?

I have suspected the vent area may be too small. The chimney does draw very well but there is probably not enough area in front of the dome to hold all the exhaust. It will be slightly larger when bricked but I think I will fabricate another vent. I do start the fire under the flue and push it in but it makes no difference. Thanks for the advice.

[Novaslo]

Re: Chimney problem?

I have the same problem. The next oven I build, If I ever build another one, I will have a very large roomie vent area leading to my flu pipe. This is the secret to no smoke. But, I will say that it gives it a used working look and at this point, I am ok with the smoke coming out the front a bit.

Onwards to the cooking.....which I can't stop!!!

[ATK406]

Re: Chimney problem?

If you build an exterior arch in front, you can keep the opening height the same as the inner arch (since you won't get anything taller than that in the oven anyway). That would create a slight chamber in the vent area under the chimney - might help. You can experiment by cutting a piece of plywood in the shape of your exterior arch and see if it helps to keep the smoke inside. The down side will be in your door design. You would have to tip the door forward (or back) to get it under the entry arch. Sorry for the rambling post...I hope you can understand what I am saying.

Regards,
AT

[rjohnson]

Re: Chimney problem?

I have re-built the vent-enlarged it with another steel version about same depth [7.5"] by about 15" long and 8" high, on top of which I welded the original one [shortened a bit to fit]. It worked much better with only a little smoke emerging and this stopped completely if I placed a piece of my original door form in front of the vent area, slightly raised to allow entry of air. My bricklayer has started the final enclosure but we have been stalled by rain. I will take more pictures to post soon. Thanks

[rjohnson]

Re: Chimney problem?

Here is the finished oven . It works well but I have been a bit impatient in getting it hot enough to maintain a hot enough temp. No smoking except initial firing