I've been running this stove for about two winters and I've had a lot of stress with back draft. Fortunatley, I had installed an inline draft inducer for when it was really not good. Even when it was working, it just wasn't pulling the way it should. I've included these photos of the top of my heat riser with the lid off - where I think the math is probably off. You'll see all the creosote build up - not good. I'm thinking the gap from the top of the heat riser to the lid is too big, but it looks like the gap around the heat riser is big enough (something I was really worried about because that's not nearly as easy to fix) - ranging from 1 to 2+ inches. You'll also see that my insulation has sunken on my heat riser, and there is about 1" difference between that and that heat riser pipe, which I plan to fill. I'm thinking the whole heat riser should be built up a bit, so the whole thing is more like 1.5" to the lid. Right now I have about 2.5" from the heat riser pipe to the lid.
I know there are many other variables that can cause this. Here are a few details: It's a 27" front feed with 20" to the beginning of the heat riser. The heat riser is 35". My chimney rises several feet above the stove outside. I get a lot of moisture dripping around my chimney - black liquid.
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
posted 6 years ago
Directly, your top gap seems good. Could be a bit bigger imho. Tho that's matter of taste. But your side gap is wayyyy too small. It should be at least 1.5 inches if not 2" If you go under the 3cm barrier, you get into laminar flow troubles. Gases stick too much to the walls of the heat riser and of the barrel. So that slows theses down.
And check your transition area. That should be big, huge even!
Im no pro at these by any means. But My opinion is that you have way to much insulation and not enuf free space for gasses for it to rocket properly. I have a little trouble partly cuz I used too small of a barrel only 12 in diameter. Im upgrading to 55 gal drum
posted 6 years ago
So, I went for it and tore apart my heat riser.
Here are a couple shots of the transition area with and without the insulation. No bueno?