What Is a Furnace and How Does It Work?

In ancient times, people huddled together around wood-burning fireplaces to stay warm. Today, home heating systems such as furnaces help keep families warm inside their homes. Furnaces are standard in homes all over the country, but what are they, and how do they work?

For over 15 years, we’ve installed and serviced various heating systems, including furnaces. At Monkey Wrench Plumbing, Heating, Air & Electric, our technicians are trained and certified in the nuts and bolts of furnaces. Thanks to our on-field experience, we’ve repaired furnaces in hundreds of homes across Los Angeles and the surrounding areas.

In this article, we’ll use our insider knowledge to review what furnaces are, how they work, and what types are available. By understanding what furnaces are, you can ask a technician important questions regarding furnace repairs or replacements without staying out of the loop.

Let’s begin!

What Is a Furnace?

A furnace is a type of heating system that is designed to provide warmth to a home. Furnaces can be ducted or ductless, but most furnaces are ducted to help distribute heat to the different rooms of a house.

This heating system is made up of various components that work together to generate warm air. Here’s a look at some of the more significant parts.

• Thermostat: Furnaces have thermostats that are the control center of the heating system. It monitors a home’s temperature and turns the furnace on when it drops below a set temperature.
• Heat source: Furnaces can have different fuel sources but generally have similar heating chambers where heat is first generated.
• Heating element: Whether it’s gas or other fuel sources like electricity, furnaces use heating elements such as heat exchangers (gas furnaces) or heating coils that create heat. The combustion areas have sensors that monitor the temperature of the heat to prevent any overheating.
• Blower motor: A crucial part of furnaces, blower motors help transport the warm air generated throughout the different ductwork within a home.
• Air ducts: Ductwork is the pathway of furnace systems. These flexible ducts allow the warm air to travel from the furnace to the different parts of a home.

Most of the parts that make up a furnace have operated the same for decades. Still, recent technological advancements have improved the efficiency of the components within a furnace so they can better convert fuel into heat. Manufacturers use the Annual Fuel Utilization Efficiency (AFUE) rating to categorize furnaces by how efficiently they convert a fuel source into actual heat used to warm a home.

In the next section, we’ll describe how these furnace parts work together to generate and distribute heat.

How Does a Furnace Work?

Furnaces typically run all year long but are more active during colder months. Here’s a step-by-step summary of how furnaces work inside a home.

• A thermostat turns the furnace on: Homeowners can turn the furnace on via a thermostat. Smart thermostats allow homeowners to monitor and turn the furnace on or off remotely from their phones through an app. Thermostats can also turn the furnace on when the temperature in the home drops below a certain level.
• The furnace starts heating up: The furnace’s burners receive a signal from the thermostat. Gas furnaces use a pilot light or ignition switch to produce a spark that creates a flame. Electric furnaces use electricity to heat special coils that generate the heat required to produce warm air.
• Blower motor starts blowing: As the heat is generated, the blower motor starts blowing air over the heating elements and then distributes the warm air throughout the ductwork.
• Air circulation: The air circulating through the home eventually cools down. Furnaces have return ducts that pull in the cooler air and recycle it through the heating process.
• Furnace turns off: After generating and distributing heat, the furnace shuts off after its sensors detect that the home has reached a desired temperature. The system remains idle until warm is needed again.

To help provide and maintain air quality, furnaces have filters that help remove debris, dust, and other airborne contaminants from the air as it travels throughout the home. These filters are categorized using the Minimum Efficiency Reporting Values (MERV) ratings, which examine a filter’s ability to remove particles based on size.

All furnaces are designed to provide warm air, but not all are the same in certain aspects.

Types of Furnace

Furnaces can be divided into their fuel source types and the number of capacity settings a furnace can operate at. When pairing a furnace with a home, HVAC technicians typically review a home’s square footage, available fuel source, and other factors to determine which furnace is suitable for that specific house.

Here’s a look at the different furnaces based on fuel source.

• Natural gas furnace
• Electric furnace
• Propane furnace

In the past, oil and coal were considered furnace fuel sources, but those options have become far less common due to their environmental impact. In Los Angeles and the surrounding areas, natural gas is the common fuel source for furnaces.

Besides fuel sources, furnaces are available in different types of staging. Staging refers to a furnace’s ability to control the maximum heating output to generate heat. Furnaces come in one of the following staging categories.

• Single-stage: These furnaces typically have one setting that allows them to generate heat at 100% of their maximum heating output.
• Dual-stage (also known as two-stage): Dual-stage furnaces have two settings, either 100% or around 50% maximum heating capacity.
• Modulating: Similar to dual-stage, except modulating furnaces can have up to 100 settings of heating capacity instead of two.

Staging allows furnaces to heat homes, but multi-stage systems offer far more control over the heating output to provide homeowners with energy costs. The different staging options and fuel sources for furnaces are major factors in determining how much a brand-new furnace can cost.

Is a Furnace Right for Me?

Furnaces are complex central heating heating systems with different parts and various fuel sources. Now that we have broken down what these parts are, how they combine to generate heat, and how they’re available in different furnaces, homeowners can better understand how a furnace works. Understanding what a furnace is and how it operates can put you in a better position to ask questions about furnaces with a technician.

At Monkey Wrench Plumbing, Heating, Air & Electric, we have years of experience working on all kinds of furnaces and seeing how their parts work together to generate warm air. We believe in educating homeowners about how specific HVAC systems work so they can confidently search for a heating system, whether it’s a furnace or not, that can keep their houses warm during cold weather.

If you want to know more about furnaces, contact us using one of the buttons below. You can also book an appointment through our online HVAC scheduler.

Now that you know what furnaces are, you may be interested in learning more about some of the top brands. To continue your search for the right furnace, check out this article on the top five furnace brands.