Great thread! I figured I would add another slant to it though
Been installing these for a few years now with great success...
Its a Garn wood gasification boiler. The concept is pretty easy, you load the fire box with wood and light it, turn on the inducer fan timer and close the door.
Once the fire is lit, the charge starts to burn and when the temps rise, it will re-burn in a secondary burn chamber. The burner is actually immersed in a 1500, 2000, or a 3500 gallon tank of water and the flue gas pipe makes 2 more passes before exiting out the back of the unit. The last one I did was direct vented and during full fire (450,000 BTU), I can put my hand under the exhaust and hold it there
You basically fire it until the tank is charged to 190 degrees and then let it burn out. Normally, a once a day firing is all that you'll need but that depends on the type of heating you have in the house, the size and of course the outside temperatures.
These boiler are not the old smoky classic outdoor boilers that you see littering the landscape and filling the valleys with smoke