How a Natural Gas Furnace System Works – The 4 Main Components

January 15, 2021

Warm living Room

A heating system is not nearly as complicated as you think, so having a basic understanding of your furnace is especially important during wintertime in London, ON when you rely on it daily. Here’s how a furnace system works with its four main components. Learn how to resolve furnace problems that you may be able to remedy yourself, how to keep your furnace running, and when to replace it.

The Main Components of a Natural Gas Furnace

Most furnace systems have four main components: a thermostat, burners, a blower motor, a heat exchanger and your home’s ductwork. We will explain how each component contributes to the system’s overall purpose.

1) Thermostat

For starters, they operate based on your home’s thermostat. The thermostat sensor monitors the temperature in your home. It is essentially the brain of your home’s heating system. When needed, it calls on the furnace system for heat.When you select a temperature or program a schedule, it tells your furnace system how hard it needs to work. 

2) Burners

Furnace burners are a set of tubes through which gas is directed and burned. Think about a gas grill’s burners. Depending on the thermostat’s temperature, the furnace will work to reach and maintain the temperature you’ve selected.

A gas valve, igniter, and flame sensor all work together to control the flames within your furnace. When the system calls for heat, the gas valves open and the mixture is ignited. Lastly, the flame sensor works as a safeguard that shuts off the incoming gas if a flame isn’t detected.

3) Blower Motor

Most furnaces have a “multi-speed” blower that is preset at the time of installation. The blower motor directs air coming from return ducts into the hot heat exchanger. Higher efficiency furnaces come with a variable speed blower that can self-adjust fan speed during operation.

This component is vital for moving air along within the furnace. If your furnace turns on, but the air isn’t being pushed through vents, you may have a problem with your blower motor.

4) Heat Exchanger

The heat exchanger is another essential part of the heating process. 

The exchanger is a thin metal shield that stands between the blower and combustion chamber. It distributes heated air from the furnace through your home’s air ducts and into rooms.

After fuel is combusted, the mixture of gas and combustion fumes is created. These are known as flue gases and are not safe to breathe.

The heat exchanger needs to be completely sealed to prevent flue gases from escaping effectively. Now you can understand why having a faulty heat exchanger can be dangerous.


We hope this article has given you a more robust understanding of how a natural gas furnace system works. There are several other components in a furnace, but thermostats, burners, blower motor and heat exchanger are the most important. Looking after some maintenance for your furnace system is possible, but we recommend leaving repairs to certified professionals.

You can see our Ultimate Furnace Heating Guide for a simplified explanation of how a furnace system works. It’s also an excellent resource for any home heating information.

Please call us in the London Ontario area whenever you need advice about your furnace at (519) 453 4650.

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January 15, 2021 11:59 am

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