how a furnace works

How A Furnace Works

You know that warm, comforting feeling when you first step inside your home on a cold winter day? The furnace has been running all day, and the house is nice and toasty. But have you ever stopped to wonder how your furnace works? 

Wonder no more because we’re here to explain it all! There’s nothing complicated about it at all, contrary to what you might think!

Keep reading to learn about the basic components of a furnace and how they work together to heat your home. You might be overwhelmed by just how much goes into keeping your home warm!

Furnace: The Home Heating Cycle

Furnaces have a sequence of operations. Recent technological advances have led to a change in the “standard” sequence of operations over the years. However, certain principles remain the same.

Here is a look at the usual sequence of operations for a furnace:

  1. A heating cycle will begin when your thermostat detects a difference between its settings and your home’s temperature. 
  2. The furnace’s draft inducer fan starts and begins pulling air into the unit.
  3. The furnace’s igniter starts heating up.
  4. Once the igniter reaches the proper temperature, it will ignite the gas in the burner assembly.
  5. The burning gas will create heat, which will be transferred to the heat exchanger.
  6. Warm air will begin flowing from the furnace and into your home’s ductwork.
  7. The furnace will continue to operate until the thermostat is satisfied and sends a signal to shut off.

Furnace Parts & its Systems

A furnace has five main parts:


A furnace works by heating air and circulating it throughout your home. The furnace’s burner is fueled by either natural gas or propane. 

The burners are where the gas or oil is burned. The burner consists of an igniter, a control valve, and a fuel nozzle. The igniter is what starts the burning process. The control valve regulates the amount of gas or oil that is burned. The fuel nozzle controls the flow of gas or oil to the burner.

Blower Motor

The blower motor circulates the air in your home. It is typically located in the furnace, near the bottom. The blower motor has a belt that connects it to the blower wheel. As the motor turns, the belt turns the wheel, which moves the air. 

Heat Exchanger

It is the part of the furnace where the actual heating takes place. The heat exchanger is a series of metal coils that transfer the heat from the burning gas or oil to the air that is being blown into your home by the blower.

Combustion Chamber

The combustion chamber is the furnace area where fuel and air mix. All combustion requires oxygen. Your furnace has a vent system to “inhale” air to create clean and efficient combustion. This venting system is also where your furnace will “exhale” the combustion by-products.


The furnace filter is a screen that traps airborne contaminants, such as dust and pollen, before they can enter the furnace. The filter helps to keep the furnace clean and prevents the build-up of dirt and debris on the furnace components. It is necessary to keep the filter clean so that it can do its job properly. A clogged one will lead the furnace to work harder and use more energy.

So there you have it – your furnace is a marvel of modern engineering! We hope this article has done something to demystify the inner workings of this essential household appliance. Have any questions about your specific furnace? Give LYNN HVAC a call, and we’ll be happy to help!

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