On a different thread we were discussing different fire types and I mentioned I have a "cachelofen" Dan asked me to describe it and I thought I'd do it in a seperate thread...here goes.
A cachelofen is a German word and I'm not too sure what it actually means! It's a masonry heater though that can burn wood very effeciently. Mine is built on three floors, so the firebox is actually in the basement of the house and it's made of cast iron with 2 doors one above the ash pan and one door for the ash pan. The idea is to build a fire and let it go through the full burning cycle without adding wood. So you lay the fire and light it from the top so that the wood "gassifies" that means the gasses are burned off first, kind of like burning a candle and once the volatile gasses are consumed all that remains is charcoal which burns extremely hot. Once the fire is to the charcoal stage the draft is completely closed and the charcoal fire will last about 2 1/2-3 hours. It's hot like the fires of hades too and with the draft closed it doesn't head up the chimney very fast so it really pours out the heat.
I've gotten a bit ahead of myself, when the fire is burning the smoke emerges out the top of the firebox then heads down into a secondary chamber where the gasses undergo a secondary burn then up the chimney to the main floor of the house. On the main floor is a largish masonry radiator where the smoke travels back and forth (horizontally) through a series of passages made of firebrick. This allows the radiator to extract the heat from the smoke before it heads up through the chimney. It then radiates the heat slowly back into the house, and once hot it will stay hot for about 12 hours. Incidentally there is also a warming oven built into this part and it's a great place to make jam, fruit leather and mulled wine.
On the top floor of the house (3rd level of the cachelofen) there is another masonry radiator that takes a heating duct from the firebox in the basement and transmits heat to the top floor of the house. The beauy of this is the cold air from the basement floor is heated and moved to the top of the house which forces the cold air down and creates a constant circulation of air in the house.
That's the basics of it I suppose, it's hard to describe and even seeing it personally most folks don't get a complete understanding of it. I will say one thing though it really burns cleanly, within about 10 minutes of lighting it you can't even see smoke from the chimney it burns that clean and hot. I used to go and cut wood but the cost of petrol is so high that it didn't make sense. So I collect unwanted pallets and cut them apart and burn them. Most are made of birch and oak so it's great firewood and I can collect it close to home.