I had not previously seen your location, SC. My previous backpuffing troubles were definitely temperature related, only occurring at outside temps above 40F. I always just assume everyone here is in a cold climate, and this could definitely be a factor, when combined with your short chimney.
I ran a little experiment over the last week, which I think might be of interest, in this thread. Some may remember me complaining a week ago, that I had burned up all the dry wood stacked near the house, and I had to go move another cord from my wood lot up to the house. What had been left at the house in the days prior to that was stuff that had been split too big to dry in the time I had for seasoning, and so it was large splits with moisture trapped in the middle. My last two loads thru my stove on the shorter chimney had been smouldering messes, and had thoroughly clogged my catalytic combuster on that particular stove. That stove was left cold all week, as I was busy with work, and figured I'd get around to cleaning it out and firing it back up this weekend.
Well, rather than pull it out and clean out the creo that was clogging the cat (no fun, anyway), I decided I'd try to burn it clean. I loaded the stove yesterday with a medium load of nicely dry walnut, medium to smaller splits. I got it going furiously, with stove top temp = 600F and single wall flue temp at 650F, before closing the bypass. The fire died out, and then the stove started back-puffing. Stove top temp quickly dropped to 450F and flue temp to 200F (or less?). I subsequently went back to bypass, got the stove and flue heated up again, and then closed the bypass. This time, the fire took a few minutes longer to die out, and then I started getting smoke gently flowing out of every crevice (air control, intake, etc.). One more cycle like this, and I eventually got the cat up to 550F. Just a minute or two later, the cat temp shot up to 1500F (indicated it was finally burning clean the creo it had been coated with the wet load the prior week), before settling back down around 900F. I only had three nicely dry small/medium splits in the stove, and 900F is a normal cruising temp for that size load.
So, I was able to generate all of the same symptoms as AppalachianStan, by simply running a clogged cat. What was of more interest to me is that one can (with some effort and pain) burn clean a completely creo-clogged cat. I don't think the same could be done with an ash-clogged cat.
