(Moderators: I have long ago embraced that perhaps I'm not the sharpest knife in the drawer, so it is possible that this posting is misplaced. Please feel free to move it wherever you feel you must, and at least let me know where it went. I'll understand.... ) I have been using old "king" coal for about 30 years. At first when my family came to this old farmhouse it took between 12 and 16 cord of wood to heat it a season. There was an old coal furnace in the cellar that we burned wood in--simply because the old man decided it wasn't in any condition for anything as hot as the coal fire it was intended to have in its belly. I begged to differ, and I was alpha enough that eventually things shaped up that I would assume all responsibility. And I did. I started advertising that I would remove unwanted chestnut coal from cellars. There were many unwanted caches of coal. Having chopped wood for enough years of my life I was not one to refuse free fuel. I used an ancient Dodge truck to haul home bummed coal from all over. For many years. I did have to start being legit, and buy coal like the rest of society eventually. I tended that furnace--merely an old and very large pot-bellied stove encased in a metal can, and originally gravity feed and later blower fed heater. This behemoth ran off of chestnut or "nut" coal--Penn's best anthracite--and needed to be shaken down, banked, shoveled out, swept of fly-ash, etc--which I did for darn near three decades.. Enter my coal dealer, who has been keeping me in coal and selling it to me far cheaper than any of the competitors for many years. Now his prices are starting to get obnoxious, but he's doing the best he can under the circumstances of soaring operating costs. The dealer had been trying to get old tight-pockets here (me) to upgrade from this mid 19th century monster to something newer. It finally happened that somebody bought an Alaska brand model 140 rice-coal furnace, and then got talked out of it by his wife, and my dealer reluctantly bought it back--barely used. I got it at a significant discount. I got it home and proceeded that winter to set it up in my mudroom. And managed to more than successfully to heat that mudroom--along with my rather large workshop adjacent to it by keeping the door open. The following summer I uninstalled the old furnace (not a small project--believe me!) and then put this new 170KBTU plant in place... It is--as originally offered by the dealer--a double-stoker unit, with each stoker controlled by a separate control box. I wanted to make this new furnace down cellar respond to a normal thermostat up in the dwelling, and was qouted a price by the maker of this furnace of around a grand for the kit to do this. I told them what they could do with this kit. The furnace came to me with two stokers--each with their own controller, each of which I assumed I was expected to control manually to try to maintain the desired rate of burn to keep my house warm. Screw that crap. I wanted a 'stat like the rest of the civilised world. I also ascertained from the Alaska stove co that one controller could not source out to two stoker. With such info I devised a system in an old alarm system box that has the relays necessary. One relay enables a single control box to control 2 stoker motors. Another relay is controlled by an upstairs 'stat--like what the rest of the world has--which switches between the two feed control boxes. So one controller "pilot" is set at a minimum maintenance burn rate, so that the fires wont extinguish. When the stat calls from above for heat the relay that answers the stat's impluse switches the stokers over to the other controller which is set at a higher stoker feed rate. So the 2 stokers are controlled by one controller at a time--slow for a pilot rate when no heat is called from the stat, and a higher rate when the stat warrants more heat. Then--conscious that when the hopper runs out of coal the fires on the stoker pads.... are extinguished, and have to be manually rekindled, that I needed to come up with a system to provide a reserve in the hopper--to wit that when the supply in the hopper dwindled from its maximum of 250lbs of rice coal to a paltry 75 or so that the thermostat upstairs would essentially be disconnected. This way the coal would be consumed at a mimimum rate until I could get back and replenish the supply. Pilot rate with the remainder is generally about 12 hours, so I have plenty of time to get around to rectifying the situation. Hillbilly Electronics to the Rescue. I whipped up a 3-transistor DC amplifier circuit, and printed up a board for this amp to use with a CdS cell (LDR) along with a 12V bulb--both planted on opposite sides of the hopper--bulb to upper left and "electronic eye" to lower right to provide appropriate slowdown of fuel consumption at the time when it is adviseable.... PC assembly.... Hopper above critical level... Hopper below critical, and the stat upstairs is ignored until I can haul my lard butt down to refill the hopper... The electronic eye is seen to the right as a pilot light jewel, in which the cell is hidden and protected. I still plan a battery backup, that will enable the furnace to maintain pilot burn during power failure, until I can get around to firing up my genset (also homebrew).... to provide a normal lifestyle until the provider can give me juice again. It will be comprised of an inverter, a trickle charge system, deep cycle batteries, and the third relay seen in the control box, which will transfer from one system to the other--as needed. Anyhoo that's how I do. How do y'all keep warm?