Lean Burn Overflow

Image you are sitting at a camp fire. The fire is burning really well and quite high. Everyone sits around watching the fire as it slowly dies down. Finally, someone gets up and puts more fuel on the fire. Now the fire slowly starts to build again until it is as high as it was before. If no one does anything, the process will repeat, thus our flame "oscillates" from a high flame to a lower flame. This is what a lean burn looks like. If someone sees the flame just starting to die down or anticipates that it will start to die down and adds fuel, the flame will remain "consistent" in height; this would be a good flame. A good flame will have a fairly consistent height and temperature. A lean burn will have two different temperatures. A high temp when the flame is higher than that needed to burn and consume the fuel totally and a lower temp flame when the flame becomes smaller. If the fuel is fed into the burn pot while the temperature is lower than that needed to ignite the fuel (using corn as an example), the corn may only char or burn maybe 70% of the kernel. The stove expects to see 99.7% of the fuel burnt leaving only 0.3% ash content in the burn pot. Now there is an extra 30% ash left over in the burn pot rather than the 0.3%. Not only is this 30% more ash, but any thing that it falls on will become somewhat insulated from the temperature of the flame. The build up of partially burnt kernels will continue to build when the flame is at its lowest temperature. As the build up begins, it normally starts to build in the front of the burn pot while the back of the burn pot seems to be burning real well and sometimes more blow torchy (like my choice of terms?). While a rich burn will build ash content as water fills a glass (level), a lean burn builds as if it were building a hill. Both a rich and a lean burn can "over flow" the burn pot. Once the pot over flows, it would be hard to determine whether the over flow was caused by a rich or a lean burn. If you observe the burn pot starting to fill up, you can tell - rich or lean. Depending on HOW rich or HOW lean will determine how fast the pot will fill up. This could happen in an hour or it may happen after 2-3 days. The 2-3 lean burn indication is triggered by the exhaust temperate differential vs time. The stove is using the exhaust temperature to see what you basically would see by watching the flame. So as with the camp fire, if you saw the flame starting to die out, you would add fuel "sooner" to keep the flame high and consistent in height. The stove is doing the same thing, just getting its' input from a different source. The 2-3 flashing lights (lean burn recovery mode) is not a cause of the over flow. I would however, not make any adjustments while the stove is flashing the 2-3 error code. The stove, whether you increase the trim pot feed rate knob OR the stove is in the lean burn mode, is adding fuel sooner in the feed cycle. Remember the camp fire? Yes we added more fuel, but the important thing is the "when" we add the fuel. NOTE: If the pot is filling too fast, you can do a manual ash dump (one dump only) by pushing the ON button rather than shutting the stove down.

Typical ash buildup of a LEAN

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