Forced-air gas furnaces are a safe and efficient way to heat your home. Although their operation is fairly straightforward, few people know how their furnace actually works. Knowing a little about the ins and outs of how your gas furnace works will help you troubleshoot problems with your system, as well as communicate effectively with an HVAC professional if service is needed on your unit.

Your furnace has six major components that work together to provide heat for your home.  The efficiency of your system depends on the optimum performance each of these components.

Your thermostat tells the furnace’s burner when to turn on and when to turn off. When your home’s air temperature goes below the setting on the thermostat, the burner turns on. When the temperature setting on the thermostat is reached, the burner turns off.

The burner in your furnace, fueled by oil or gas, creates combustion gases. These hot gases circulate through the heat exchanger, and the exhaust gases are vented outside.

Heat Exchanger
The heat exchanger is a metal box around which cool air flows to become warmed.

The blower assembly in your furnace brings in cool air from the home and sends it to the heat exchanger to be heated. Once heated, the air flows into the warm air plenum on the output side of the system. The blower then sends the warm air through your ducts and into your rooms. The blower compartment houses the air filter, which prevents dust buildup from causing damage to your system. The air filter should be checked every month and replaced when it’s dirty.

There are two types of ducts in your home. The cold air, or return, ducts provide air to your furnace to aid in the combustion process and to be warmed for your home. The warm air, or supply, ducts send the warm air to your rooms.

The registers in your rooms can typically be manipulated to control the direction and flow of air.

Proper maintenance of these major components of your furnace is essential to keeping your system operating safely and with energy efficiency. A yearly tune-up by a qualified HVAC professional will include the inspection, cleaning and servicing of each of these components.