Eyman HVAC professionals use the furnace’s order of operations to systematically diagnose problems with your gas furnace and save you time and money.
The Main Parts of a Furnace
All furnaces consist of 4 main parts.
- Burners that deliver and burn fuel.
- Heat exchangers that keep your breathing air and the combustion process separate.
- A blower that circulates heat through the furnace and distributes it throughout the house.
- And a flue that releases gaseous byproducts to the outside.
Every furnace is equipped with safeties, electrical components, and controls that create a safe heating process.
Order of Operations for Your Furnace
- Turning up the thermostat initiates the process.
- From the thermostat, an electrical current runs to the furnace’s brain, an electronic circuit board, signalling it’s time to switch on.
- Next, a series of safety switches, if closed, allow the inducer motor to start operating.
- The flame igniter starts.
- After a short delay, the gas valve opens to allow gas to the burners, and ignition occurs, starting the combustion process.
- Open safeties signal the furnace that combustion has not begun. This means gas could be building up in the system, so the safety will close the gas valve.
- During normal operation, natural gas fuels the flames, while electric gas current continues to run the inducer motor.
- Using negative pressure, the inducer motor draws the burner flames into the heat exchanger, causing it to warm.
- The blower motor begins slowly circulating air around the heat exchanger, so it will absorb the heat being produced.
- Exhaust gasses from the burners are vented outside through a flue.
- Warm air then flows back into rooms through ductwork.
- When the thermostat senses that the temperature setting has been met, the furnace rests until the next cycle.
Learn More About Furnaces and HVAC Systems
Check out our entire series of videos about all the HVAC systems in your home.
Eyman’s team is here to keep your home comfortable and energy efficient, year round.