Coal-Fired Furnaces and Boilers
At one time, coal was commonly used to heat homes. As other cleaner, more convenient fuels became available, most home heating systems were converted to burn either oil or gas. In parts of the country, particularly the northeast, some older homes still have their original heating systems designed for coal, but the vast majority have been converted to more modern fuels.
In coal systems, coal is burned in a firebox which is slightly larger than the combustion chamber of an oil burner. The larger size of the combustion chamber causes these conversions to be inefficient because energy is wasted heating an oversized chamber. Heat produced in the combustion chamber is transferred through a heat exchanger to the distribution medium, warm air, hot water or steam. Combustion gases and smoke are vented to the chimney much as they are in oil furnaces. In some homes, coal is still burned as a supplemental source of heat.