I had to do a little poking around in the firebox today, I had a few clinkers to pull out. After doing that, and shaking down the ashes, I only had about 1/2 a firebox of coal left. I put on a couple shovels of UAE's finest, let it get to temp... put on a couple more, let those get up to temp, then fill the hopper.
About 20 minutes later, I smell the fresh scent of curing stove paint. I go down to check the stove, and the fire is ROARING, the secondary burn flames were the whole height of the door. The 2x wall Duravent DVL was SMOKING and I gave it a quick shot with the infrared -- 620 Degrees!!!
I promptly turned the t-stat back, cutting off the air to the fire. I stepped outside and there was smoke billowing out of the chimney, probably soot from the bitty I had been burning last week catching fire. Luckily, within a few minutes, everything was back to normal and I'm here typing this message.
So anyway, I thought these bi-metal t-stats were supposed to be "set it and forget it", but at the higher settings, it seems to have a very nasty tendency to want to overshoot after re-loading. I guess from now on I will have to dial the 'stat back when loading if the air flap is open too far.