Forced-air furnaces are one of the most common and popular choices for heating your home, and with good reason. Forced-air furnaces are the most energy-efficient and comprehensive choice for keeping your home toasty in winter. Learning how these furnaces work can help you choose the right model for your home.
A forced-air furnace works by burning gas in the heat exchanger. A fan blows air across this exchanger, heating the air and then sending it through the air ducts into your home. When the gas is completely combusted, the flue gases move through the heat exchanger and are vented outside the home.
Efficiency levels
Forced-air furnaces come in two main types, an 80 percent efficiency model and a 90-plus efficiency model. The difference between the two lies in the way that they process and vent combustion air. An 80 percent furnace has one heat exchanger, and connects to your existing flue pipe or chimney to vent 20 percent of the air outside the house, keeping 80 percent of the heated air indoors. A 90-plus furnace has two heat exchangers, using outside air for combustion and venting less than 10 percent outside the home.
Burner settings
Of these two efficiency models, there are single-stage, two-stage, and modulating furnaces available. "Single-stage" means that the burner uses only one level of heat, "on" or "off." "Two-stage" furnaces have a microprocessor that controls a burner using two levels of heat, high and low. A modulating gas furnace does not come in 80 percent or 90-plus models, but operates at 95 percent or above. These furnaces use a microprocessor to regulate the burner at variable levels, adjusting accordingly to use the least energy possible for the optimum output of heat.
Blower speeds
Furnaces also have two blower speeds. A standard blower blows at a fixed speed and regularity, while a variable-speed will save you money on your electricity bill by adjusting to the heating needs of the house, often improving air circulation and maintaining steadier indoor temperatures.
For more information on furnaces and other home comfort needs, contact Air Assurance, serving the Tulsa area since 1985.Our goal is to help educate our customers in the Tulsa and Broken Arrow, Oklahoma area about energy and home comfort issues (specific to HVAC systems). Image courtesy of Shutterstock