I know this thread is old, but we had the same problem and I wanted to relay the solution that worked for us. The problem occurred when we switched from a boxwood stove (worked well) to a potbelly so we could burn coal more easily. We are behind in wood cutting, and we are in WV with readily available house coal. We also have a coal furnace in our basement, so coal is nothing new to us. We have used wood and coal fires for YEARS, and got the potbelly---then Super Smoke happened. Hubby was infuriated, thought it was the stove because the other one had worked well. First firing it worked well, 2nd and 3rd were smoke disasters. Weather conditions were unchanged, still air, and we were getting horrific backdraft. I was extremely : ( and being the resident pyromaniac, it was up to me to fix the problem FAST or freeze. We checked absolutely everything--still smoked.
What happened, and I can easily see this as common, was the placement of the damper placed in the flu pipe. The boxwood had a ROUND opening, with the damper as part of the stove just where the smoke pipe attached to the stove. The potbelly has an oval opening and the damper is placed in the actual pipe further up from the stove/pipe attachment. When you squeeze to fit the oval exit, the round pipe will fit---and it gradually returns to round before it attaches to the next piece of stove pipe. The damper was placed about 4" from the next section of round stove pipe. The pipe isn't exactly round, even though it looked it at that spot. What happened was that the damper got stuck after the 1st firing. It appeared to be open, but, was actually shut--thus we weren't getting backdraft at all! It sounds so stupid, but, it appeared the damper was open--yet it was jammed a little and smoke couldn't exit. I decided to wiggle the damper to ensure something wasn't stuck on it (even after new installation I was making sure) and I could feel that it was jammed. A little wiggle more and waa-laa---proper draft.
Stupid self-inflicted issue, but I could see this easily happening to others.
Learn from our lack of attention to basic details! It hammers home the fact that draft/smoky stove issues are rarely caused by the stove--it's the draw/chimney that needs attention.
