Published: November 30, 2008 11:27 pm      

Furnaces’ operation is simple

Outdoor residential furnaces – which create heated comfort for their owners and can cause consternation to neighbors – are of a simple design geared for burning wood or coal.

With an average dimension of 4 feet wide, 6 feet deep and 6 feet tall, there are dozens of brands that can heat an area of about 5,000 square feet, according to trade industry literature.

While designs vary, they are basically a fire box enclosed in a water jacket, surrounded by insulation with venting through a smokestack.

As the home calls for more heat, a sensor in the furnace activates the draft blower, which intensifies the fire. It’s at this point that the smoke produced is at its heaviest.

The logs, which usually can be 30 inches or so in length, or the coal on some models, is loaded through a front door, or a hopper toward the top, as with the Hampshire Easy Loader, now being manufactured at Corle Building Systems in Imler.

Typically, the furnaces are located outside, between 30 to 200 feet from the home, and pipes are buried underground.

One pipe moves the heated water into the home where it circulates through the home’s heating system. A second circulates the water back to the furnace for reheating.

The concept is to produce a slow, cooler fire, maximizing the fuel and the heat transfer.

Working in conjunction with the U.S. Environmental Protection Agency, furnace manufacturers – including Corle and Mahoning Wood Stoves of Mahaffey – are looking for ways to reduce the smoke and odor.

Many stoves are being built with a reburn area to sharply reduce the gas buildup that has been escaping into the environment.