Well, looks like I got burned, so to speak!
I've been burning some buckwheat size coal from GregL since Sunday mid day, and up until last night, it was running beautifully.
Went to bed around 10 last night, everything was running fine - but then I woke up at 12:30am to the most awful stench in the house
. I ran downstairs to see what was going on and at first glance, the stove looked normal, but a second look around the back showed where I could see glowing heat at the hopper/stoker interface. Oh SH!T!
I spent the next couple of hours digging out the hopper and pushing the burning coal down the grate and into the ash bucket. I pulled off the hopper and started taking the stoker apart. The nylon cam was a puddle of goo, and the nylon screws were in a similar condition. The felt insulation sheet between the stoker and the gear motor mount was well crisped, and was responsible for much of the stench. Probably a good thing as that is what woke me up. Fortunately, there doesn't appear to be any other damage or discoloration due to the heat, and the stoker motor is fine.
The CO detector which is 12 feet away never registered any CO (digital display), and there wasn't even any coal gas smell - the direct vent was sucking all the fumes into the stove. All I could smell were toasty stoker parts.
I called Keystoker this morning to order a new cam - and discussed the problem. They stated that buck shouldn't be burned in a direct vent stove (and Don had told me that once before, also). Of course, being the smarty pants, I thought I had this stove dialed in perfectly with the draft, etc. so why should it make a difference between DV or regular vent? Well, obviously it does, and with the larger coal size, it was able to pull enough air down through the hopper to let the fire burn back. With the rice coal, it never even hinted at trying to burn back.
It also doesn't help that the stove idles much of the time, which gave the fire the time to burn back. At higher fire rates, the coal would likely be pushed down faster than it could burn back..
So, I'm down until my cam gets here, and will have to mix the buck in with the rice to avoid duplicating this scenario. Live (a good thing) and learn....