starcat evaporator question

[tapdrinker]

Hi Everyone.
My starcat evaporator-First boil of the season-I had a flame coming out my chimney about 3-4' and the chimney is already 6'. It looked like a rocket stove or whatever they call it.
Do I need to add more pipe? I'm thinking since I have no issue with the flame coming out as there isn't anything burnable nearby. Are arches supposed to have that much flame?


https://www.youtube.com/watch?v=PjSvUTZUMGw&t=4s

[ecolbeck]

Short evaporators often have that phenomenon. It happened to me on my first setup which was a 2x3. Blowers can make it more pronounced. I think the only real issue is wasted fuel. Perhaps your stack will have a shortened life span? I wouldn't add more stack.

[maple flats]

The flame you see coming out of the stack is not likely flame from in the firebox traveling that far. Many evaporators have flame out the stack (as my 3x8 did before I added Air Over Fire). The reason is that the oxygen is used up but there's still unburned wood gasses and enough heat, and those wood gases re-ignite as they get more oxygen. A taller stack won't help unless it's tall enough to drop the temperature below the ignition temperature. The only way to fix it is to add air over fire (AOF). Read a study on the university of Vermont about combustion efficiency. This isn't something you would be likely to do for this season, but if you think the evaporator you have will be what you will be using 3-5 years out, think about it. You could use a small bounce house blower for the air pressure needed.