I'm new to the forum; but by no means am I new to coal-fired heat.
I grew up in a funeral home (hence, the screen name) in which I learned how to curse like a sailor while helping my Dad babysit a Yellow Flame flat-grate stoker boiler. The stoker was a royal PITA; so when the boiler finally sneezed (RIP 1958-1993), there was no sadness as my plumber (George Maberry) trucked it out of the basement; making room for an EFM 520.
The 520 runs smoothly on rice, with virtually NO repairs (a worm) since 1993, burning about 12 tons a year to heat a building that dates back to 1858.
When we bought the duplex commerical/residential building next-door, both chimneys were shot; and I wanted to install one unit to do the whole place. We consolidated the building into ten zones (two radiant floor, two cast radiator; six finned copper). To handle the load, I was sold on EFM, so we chose a new EFM 900; and had it professionally installed by a dealer in 2002.
The 900 is (to say the least) a lot more cantankerous than the 520; and I have two problems.
PROBLEM 1: For those of you familiar with this beast, the pot rotates and the fines are automatically discharged by a slotted cylinder below the pot. The transfer case that drives these two functions chewed up its two top bearings -- shearing the pin as it locked up the whole mechanism. I got a machinist friend to fix the transfer case (installed new bearings; manufactured a new shaft). But as my Dad's experience taught me, the only time a stoker breaks is: 1) on a Holiday, or 2) when it's -10°. As such, I'd like to have another transfer case as a spare; so I can easily swap out the bad part while it's being repaired. Anyone have one laying around? Working or not?
PROBLEM 2: When the 900 was first installed, it was burning rice. I quickly found out that buckwheat was the preferred coal size; and moved to buck soon after install. But even with a dealer/professional set-up, I've never seen the "optimal" EFM fire that is so easy to attain in the 520. And while I'm currently set up to maximize coal burn, I still get partially burned coal in the ash. (Compared to the 520, which often produces an ash almost similar to the kitchen coal stoves of old). I've increased the air from 6.5 (set by the dealer) to 8.25, and got an improvement in coal burn. But it doesn't seem to be enough; and it's just starting to make clinkers, even at that air setting. Further, during cold-snaps, I can't seem to get the 900 to feed more than 6-7 teeth without walking the fire off the pot. I buy coal for both units from the same breaker; so coal quality isn't the issue. Can someone please tell me how to adjust the fuel-air mixture on this puppy?
The funny thing about this whole experience is that the dealer said at one point,
"Well, it's more likely to break when it's cold."
I commented that my brother is a roofer, who always says to customers who complain about leaky roofs,
"C'mon, it's not so bad. Your roof only leaks when it rains."