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October 26, 2023

How Do Furnaces Work?

A technician removes the cover from a gas furnace

Living in Ontario means enduring bitterly cold winters, which is why reliable heating solutions are a must for every home. They start with a furnace. Yet, despite them being in every home, most people don’t know how they function.

So, how does a furnace work? How does a gas furnace work and is it different from how an electric furnace works? What about oil furnaces?

We’ll answer these questions and more as we break down the inner workings of a furnace, demystifying its operation and explaining the key components that make your home a warm and welcoming haven during the cold winter months. 

Let’s get into it! 

What Is a Furnace?

There are different types of furnaces depending on the fuel source and the efficiency rating.  The most common are gas furnaces, oil furnaces, and electric furnaces—they all heat air and distribute it throughout your home using ducts and vents.

Furnace fuel efficiency is measured by its Annual Fuel Utilization Efficiency (AFUE) rating, an indicator of how efficiently it converts fuel into heat. Higher AFUE ratings mean greater energy efficiency for additional cost savings and a reduced environmental impact.

But how do furnaces work to create this heated air? We’ll answer that next!

How Furnaces Work

All furnaces need a fuel source to heat and distribute warm air throughout your home. How oil furnaces work is similar to how gas furnaces and electric furnaces work—the type of burning fuel they’re using is the only difference.

Essentially, what happens is they draw in cold air, pull it through the ducts, heat it using their specific fuel source, and then circulate the resulting warm air to your home.

As such, regardless of what type you have, something has gone wrong in this process if your furnace isn’t working. That’s when we recommend calling the professionals to assess the problem in order to get your unit back up and running.

 A man removing the air filter from a furnace

Understanding Furnace Parts

How does a furnace work with so many parts? It’s a valid question. 

We’ll narrow things down to the main components in this section to give you a concise flow of how a furnace works to convert cold into warm air: 

  • Return Register and Duct: These work together to pull cold air from your home and store it inside the furnace. 
  • Air Filter: This small yet crucial part filters all sorts of airborne contaminants and pollutants.
  • Gas Valve Control: This part works as a monitor in gas furnaces and regulates the fuel pressure travelling to the burners.
  • Blower Chamber: This holds the furnace blower and blower motor together, which blows warm air through the supply ductwork.
  • Burners: These are essential to how gas and oil furnaces work; they’re responsible for creating fire by pulling fuel from a gas line or oil tank. 
  • Pilot Light or Electronic Ignition: Old model furnaces use a constantly running pilot light to prepare the furnace for work. Newer models use an electric ignition that receives a signal from the HVAC system when your home is ready for heating.
  • Flame Sensor: This small rod detects if fire is present in the burners. It shuts down the entire system when there’s no heat to protect you from potential gas leaks.
  • Heat Exchanger: This component safely transfers heat from the burners. 
  • Supply Duct and Register: This is where the heated air exits the furnace and enters your living space.

The Heating Process Explained

Now that you know the basics of how a furnace works, let’s dive further into the furnace heating process that keeps your home warm during colder months.

  • The cycle starts when a change has been made to the thermostat as this signals the furnace to turn on and ignite the fuel in the burner. 
  • The flames in the burner warm the heat exchanger, which transfers heat to the air passing through it. 
  • The blower fan then pushes the now-warmed air out into your home through your ducting and supply vents.
  • The return vents collect the cold air and recycle it. This process continues until the thermostat signals the furnace to shut down.

 A person adjusting thermostat settings using a smartphone app

The Role of Thermostats

How does a furnace work without a thermostat? If this is something you’ve been wondering, then we can provide a simple answer—they don’t!

Thermostats are the nerve centre of your home’s heating system. These devices control when and how much heat the furnace should deliver to meet the desired temperature.

A modern furnace paired with a smart thermostat can also:

  • Keep your home cozy and comfortable by regulating furnace output
  • Save energy and money by lowering the temperature when you don’t need it
  • Customize your heating schedule to fit your lifestyle with programmable features
  • Connect to Wi-Fi networks so you can control your thermostat from anywhere in the house with your smartphone 
  • Learn from your habits and optimize your heating patterns 
  • Protect your home from overheating by shutting off the furnace when it’s too hot

Stay Warm This Winter With LG Home Comfort

If you were looking up: “How do furnaces work?” “How does a gas furnace work?” “How does an electric furnace work?” or “How does an oil furnace work?”, then we hope this article answered all your questions.

LG Home Comfort understands the importance of having a warm and snug home. Whether your gas furnace needs a check-up, your electric furnace is acting up, or your oil furnace could use some TLC, we have the solutions you need. Our team of industry-trained technicians will keep your heating system working efficiently all season long!

We offer a range of heating services for your 360° comfort, including:

Get a quote today or call us at 1-866-530-5442 to learn more!

Terms and Conditions

  • Once an initial service has been completed, the customer will be on a one-year commitment
  • After the initial 12 months, the contract will be renewed on a month-to-month cadence
  • If a service is completed for the next year, it automatically renews the commitment for an additional year
  • Customers can cancel at any time after the 12-month initial commitment as long as the following year’s service has not been completed.
  • Customers need to provide 30 days written notice in order to cancel their plan