When the thermostat sends its signal to the furnace, the furnace gas valve opens and ignites the burner component beneath the combustion chamber. The gas valve works with the thermostat to regulate the amount of gas that flows into your furnace.
Replace the furnace filter at least once every 90 days (set reminders to check the filter every month). Write the date of replacement on the filter itself so you know exactly how long it has been since the last filter change-out.
Understanding how your furnace works will help you troubleshoot your furnace and potentially avoid an expensive HVAC service call. Sometimes, you can quickly solve the problem yourself. Other times, you can easily show the problem to your HVAC technician, saving time and frustration. You'll also impress the technician.
As we head into winter, it's a good idea to learn a thing or two about the machine that will provide us with heat and comfort throughout the cold, winter days—most likely, a gas furnace. The more you know how a furnace works, the better you can troubleshoot it if something goes wrong. And since space heating accounts for roughly 45% of energy bills paid by U.S. homeowners, it's no wonder why people want to know more about how they work (U.S. DOE).