Most home comfort systems have two parts: an outdoor air conditioner or heat pump, and an indoor unit, a furnace. Furnaces heat and circulate warm air in the winter. They also take cool air from the outdoor unit and circulate it through your home in summer. The indoor and outdoor units are designed to work together. When the furnace is properly matched with a heat pump or air conditioner, you enjoy maximum efficiency and extended system life. Furnace heating ability is measured with an Annual Fuel Utilization Efficiency (AFUE) percentage. A higher AFUE percentage indicates a more efficient furnace.
The basic components of a furnace system are:
A Burner, where gas (natural or propane) or oil is delivered and burned
A Heat Exchanger, where the heat from the burning gas is transferred to the air distribution system
Ductwork to transfer the heated air throughout the home
A Flue or Vent Pipe, to exhaust byproducts of combustion (such as water vapor and carbon dioxide) outside