In my research to come up with an alternative heating solution to electric heat pumps, I discovered outdoor wood-burning furnaces that used hot water to warm a house. We immediately invested in a unit from Central Boiler. While a bit expensive, it appeared to be among the most efficient units to capture heat from burning logs (and no splitting required, an added bonus). We used a local dealer to install the furnace, who added new meaning to the word "laid-back".

Various stages leading to setup of the furnace. The night before the furnace was delivered, I dug a 50 foot trench 2.5 feet deep to hold the insulated water lines that will extend from furnace to basement. Delivery of the furnace was an adventure because it was in mid-March and the truck arrived after the ground had thawed. The truck was so heavy that it got stuck and took another tow truck to bring it out. Needless to say, the truck churned up a lot of mud and left some seriously compacted tracks that I'm still trying to repair. click on photos to see larger image

We are very happy with the furnace because the house not only is nice and warm, but we are paying a lot less for the heat. The furnace is a marvel of enginnering. The firebox (4 x 4 x 5 ft.) is surrounded by insulated steel walls that form a jacket holding approximately 400 gallons of water (added with a garden hose through a capped opeing in the roof). When wood is added, the fire heats the water to 185^oF. When this temperature is reached, a thermostat in the water jacket triggers a magnet in the door to close the vent feeding air to the fire. Any flames are immediately quashed and the wood smolders until the water temp cools to 179-180^oF, at which time the magnet goes into action and opens the vent to reignite the fire. The control of the fire is amazing!

Furnace fired-up with insulated sleeve containing water lines still exposed. The woodpile in the background is just getting started.	Two sets of water lines go underground to the house, one going into the basement (photos at right) and the other (arrows) into the attic air-handler.	Water lines from the furnace are connected to the water heater. A copper jacket keeps water from furnace separate from the heater.	Water lines circulating hot water through the coils of the newly-installed heat-exchanger (arrow).

Two pumps are mounted on the side of the furnace. One circulates water into the basement water heater and air handler and the other circulates water to the air handler in the attic. The pipes carrying the water are insulated by a foam jacket outside the house to minimize heat loss. They are set up to heat water and to pass hot water through a heat-exchanger placed in the air handler (pushing the heated air into the house). It didn't take long to adjust to hot water at 185^oF!

Of course, the furnace needs fuel, and lots of it -- an average of 10 cords from October through April. With a number of opportunities to acquire timber, especially after a couple of severe wind storms that felled large oak (see photo above), cherry, and elm trees, I got a bit carried away cutting, transporting and stacking wood. I now keep between 65-75 cords in storage any given year. The truck I purchased after trading in my little green VW beetle (a sad day) started out without a dent or scratch -- after two seasons of work, the bumper is gone, the back window has been blown out twice (I replaced it with plexiglass to save money), and the truck bed looks like it was clobbered with football-sized hail. I now classify this truck as my "farm vehicle" -- and it looks it! While this heating method requires considerable work, it also has helped me to become the fittest I have ever been -- sore muscles and all.