How Does My Gas Furnace Work?

A home’s furnace is a critical part of any HVAC system and is important to your family’s health and well being during the cold months. The team at Design Air is here to keep your furnace running at peak efficiency and help you understand furnace basics. Below is a general description of the major components in the heating cycle and how they operate to keep you safe and comfortable.

The Individual Parts

The Inducer Motor: A small motor responsible for pulling combustion air through the furnace’s heat exchanger(s) and properly venting the exhaust and fuel byproducts outside the home.

The Pressure Switch: A safety device responsible for measuring the level of airflow created by the inducer motor.

The Ignitor: There are two styles of ignitors: a pilot light or a heat source ignitor. Common in older furnaces, the pilot light contains a small gas flame which stays continuously lit and ready to relight the burners when heat is required. In contrast, newer furnaces use electric heat source ignitors (HSI). With the help of a flame sensor (a localized gas sensor), the HSI ignites the gas with metal rods heated to 1,800°F to 2,500°F.

The Gas Valve: A regulator controlling the flow of fuel to the combustion chamber.

The Combustion Chamber: A chamber where fuel is mixed with oxygen and burned.

The Heat Exchanger: A series of metal tubes designed to transfer heat created in the combustion chamber to cold air without the exchanger.

The Blower Motor: A motor responsible for moving the heated air produced by the heat exchanger through the ductwork to heat the house.

The Process

For both natural gas and propane furnaces, the heating process begins with a call for heat from the thermostat. When a room dips below the set temperature, the thermostat signals the furnace control board to begin the heating cycle. The control board sends signals to start the inducer motor. The safety pressure switch closes once the inducer’s proper drafting has been confirmed. The ignitor is then signaled to heat up and the gas valve opens allowing gas into the combustion chamber. As the fuel and oxygen mix and begin to burn, the heat created travels to the heat exchanger which in turn heats the surrounding air. The furnace’s blower motor initiates and moves the heated air through the ductwork to heat the home or specified area.

When the set temperature is satisfied, the thermostat signals the control board to close the gas valve and shut down the inducer motor. As the heat exchanger cools down to the appropriate levels, the control board turns off the blower motor until the next call for heat.

With the important function of a furnace, it is necessary for each part to work at a premium level to keep you warm during the heating season. Call the Design Air team today to schedule your furnace’s annual maintenance, repair, or replacement to ensure your family’s comfort during the upcoming cold season!

Contact us today at 4056.251.7997 or request service online.