The pellets in a pellet stove are cast off sawdust, wood shavings, maybe some bark, and various wood scraps from sawmills and other lumber operations. Instead of just disposing of them someone came up with the bright idea of pressuring and "extruding" them through a small orifice. What comes out the other end is what most folks would call Rabbit Food. (uh, please don't feed it to your rabbits, it's just an expression...)
The cool thing about this rabbit food is that it has a consistent size and low moisture content, which translates into efficient burn characteristics. It's kind of like someone spending the extra fifty or hundred bucks per cord of wood to have it kiln dried (and then, of course, keeping it in a dry location). As of this writing a ton of pellets costs around one hundred thirty bucks. A ton is equivalent in heating output to a cord of wood.
So now we have handfuls, actually bags full, of perfect little wood pellets just itching for combustion. To light our stove we squirt a little "starter" goo on the pellets in the crucible to help it to take off quicker. Newer stoves feature auto-ignite.
You load pellets into an attached hopper that holds from forty to eighty pounds of pellets (bags are usually 40lbs each). At the base of the hopper, pictured above, is the small motor and gear box that drive teh screw auger. The auger is slowly turned and in doing so moves (screws) the pellets from the hopper to the stove through a small pipe.
Some stoves auger the pellets up an incline where they drop a few inches into a burn pot. Our stove pushes the pellets up from the bottom of a burn pot. Each approach has it's own considerations. Bottom feeders have to have extra safety measures to ensure the fire doesn't work it's way back into the hopper. For example the pellet hopper is sealed so there's no back flow of air and flames.
The pellet "droppers" have no way to push things out of the crucible. Pellets drop in and when they burn up the ash is blown clear. If a little ash gets left behind it can get stuck or eventually fuse with more ash, forming clinkers.
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