How Are Wood or Coal Furnaces Built?
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How Are Wood or Coal Furnaces Built?
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Some furnaces provide heat by burning wood or coal. They can be a simple fireplace insert or a complicated unit with computer controlled combustion. Some wood/coal burning furnaces even supply hot water to the home as well as heat. While a wood burning furnace can be home-built it is a better idea to purchase and install a unit built by professionals
Construction
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Many of us have memories of the pot bellied stove warming us on icy days. Modern furnaces have evolved from the simple cast iron heater of yesterday. Modern wood/coal furnace construction Water cooled insulation and computerized electronics provide control over combustion so that wood or coal is nearly completely utilized.
The flame is regulated to burn at approximately 1100 degrees . This causes near complete combustion of the wood or coal along with the gases released from the fuel. The result is an almost smoke free exhaust out the chimney. This system is eco-friendly because of extremely low pollutants and greenhouse gas emissions. That is important because the EPA has regulations regarding home wood furnace emissions.
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Firebrick
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Modern wood or coal burning furnaces have a lining of high temperature firebrick inside the firebox. This insulation keeps the heat inside the unit and protects the cast iron body of the firebox from heat damage. Many units are water cooled with the resulting warm water used to transfer heat to the home.
Putting it all together
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The heart of a modern wood furnace is the firebox. This cast iron box is equipped with heavy grates to hold the logs or coal. Indoor furnaces have double wall insulation surrounding the firebox to keep the outside of the heater cool.
Dampers, blowers and electronic control units direct the air into the heater. First the air is preheated and the forced into the firebox from front to back. By carefully controlling the amount of preheated air coming into the chamber an optimum burn temperature of 1100 degrees is maintained ensuring a long slow burn. By being so efficient the amount of fuel needed is greatly reduced.
Heat from the furnace is directed through shielded water pipes or air ducts and into the home. There the heat is either transferred to under floor radiant heat pipes or into the ducting and into the rooms. Often the hot air from the heater is transferred through an existing furnace unit so that heat output is thermostatically controlled.
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