101 Guide: Get To Know Your Furnace

As a homeowner, knowing how your home's systems work is key to maintaining comfort and safety, especially during winter. Your furnace plays a crucial role in this, effortlessly keeping you warm—until it doesn't. Being familiar with your furnace means you can quickly identify issues and know when it's time to call a professional. This guide will help you recognize common furnace issues and offer preventative maintenance tips.

In Portland and nearby areas, furnaces are a popular heating choice. That's why we've created this comprehensive guide to help you understand the heart of your home's heating system.

In this guide, we'll cover:

  • Types of furnaces
  • Parts of a furnace and how they work
  • Common furnace problems
  • Furnace maintenance: why is it necessary?
  • Energy efficiency tips
  • When to upgrade your furnace

By learning about your furnace, you can extend its lifespan, reduce repair costs, and ensure it runs efficiently for many years. Let's dive in and help you become a savvy furnace owner.

Have questions about your furnace problems? Contact Four Seasons Heating and Air Conditioning for answers!

Our good service and fast response times mean you never have to wait for furnace repair. Ask about our furnace maintenance services to get an annual repair checklist customized for your unit.

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Types of Furnaces

Furnaces are one of the oldest methods for providing reliable heat to residential and commercial buildings. A furnace heats air and distributes it throughout your home. Centuries-old versions relied on coal or wood to provide heat, but modern furnaces can run on a variety of fuel sources, and there are even electric options.

Furnaces may differ based on how they work and the fuel used to power them. Most homes in the Portland area have a furnace system that includes the necessary ductwork to efficiently deliver heated air. When looking at a furnace to install, pay attention to the AFUE rating to see how well the furnace translates fuel to heat. Each fuel source has variable efficiency, making some more affordable to run than others. Let's take a look at the most common, up-to-date options.

Gas Furnaces

Gas furnaces run on natural gas or propane and are very energy efficient. High-efficiency options have AFUE ratings that indicate the furnace can translate at least 90% of the fuel burned directly into heat for your home, while a standard unit is around 80%. For many Portland homes, gas furnaces are one of the most affordable ways to keep your home warm throughout the winter.

Electric Furnaces

Electric furnaces, which are different from heat pumps, use electric coils that generate heat in much the same way an electric oven functions. The heated coils heat the surrounding air, which is then blown throughout your home. No combustion means no need to worry about ventilation for your heating system or possible carbon monoxide buildup. Electric furnaces translate 100% of the energy used into heat, which means the price of electricity versus natural gas in your area will determine which is cheaper to run.

Oil Furnaces

Oil furnaces are a legacy system that may be considered old or obsolete, but there's no one-size solution for heating a home. Oil-burning furnaces can be a cost-effective heating solution in some areas, particularly for larger homes. However, keeping these furnaces in good repair is important since older models may have an AFUE rating of only 50% after years of use.

Dual-Fuel Furnaces

While more expensive to buy, dual-fuel furnaces automatically switch between electric and an alternate fuel, depending on the amount of heat you need. These systems are some of the most efficient available, combining the benefits of electric heat with the speed of a fuel-burning system.

Parts of a Furnace and How They Work

No matter what fuel source gives some oomph to your heat and gets your home warmed up, there are some parts of your heating system that they all have in common. Below is a short list of the options and parts that are most likely to break down and have you calling for furnace repair help.


The thermostat is the device inside your home that tells the furnace when to start running. It measures ambient temperature and tells the furnace to turn on when it drops too far below the desired temperature. If you set your thermostat to 72 degrees, whenever the thermostat gets a reading that's lower than 70 degrees, it will send a message to the furnace to turn it on. Smart thermostats go even further by letting you set a timer to save you money during the times when no one is home or after everyone is in bed.


There are several types of furnace burners, but they all do essentially the same thing — burn the fuel needed to generate heat. In the burner, fuel mixed with air is ignited, which provides the heat needed to warm the surrounding air.

Heat Exchanger

In the burner, the fuel ignites, leaving behind dangerous gases that vent outside your home. To transfer the heat, furnaces use metal shielding, called the heat exchanger, between the combustion area and the air circulating throughout your home. Air moves across the surface of the heat exchanger and warms due to the heat produced in the airtight burner. That warmed air, free of flue gases, then moves through your home to warm it.


The blower is essentially a high-powered fan that moves the heated air from the heat exchanger through your ducts and into each room of your home.

Ventilation System

Since combustion often depends on natural gas — a toxic chemical — and may produce toxic air after burning any fuel, ventilation is an important part of your furnace. It often consists of pipes that run to the outside of your home directly from the combustion chamber. There are many types of ventilation systems with various safety ratings.

Common Furnace Problems

When it's the middle of winter, the last thing you want is to make an emergency call for furnace repair. Any part can develop problems, but we've listed some of the common issues that may crop up while you're running the heat.

Pilot Light Issues

Your pilot light should always be a solid blue flame. If it flickers or moves, that's a sign that your heat exchanger might not have an airtight seal. Changes in flame color can indicate the same. If you notice anything different about your pilot light or it doesn't come on automatically, it's time to call an HVAC professional from Four Seasons.

Ignition Problems

If your home is cooling off and all you hear is a clicking noise from your furnace, it could indicate a problem with your igniter. Newer furnaces have an electric ignition that uses an electric spark instead of a standing pilot light to start combustion. A dirty or malfunctioning igniter is a fairly common issue.

Airflow Obstructions

You know about the importance of ventilation for your furnace. Dirty air filters and clogged ducts or vents can all make your furnace work harder and reduce the amount of heat. Keep your system clean to get the most out of your furnace.

Thermostat Malfunctions

A frozen or unresponsive thermostat means your furnace won't turn on properly. A furnace depends on the thermostat to tell it when to start heating. If the thermostat is malfunctioning, it might cause the furnace to run nonstop, fail to turn on at all or start and stop without reaching your desired temperature.

Furnace Maintenance: Why Is It Necessary?

Keeping your furnace in good repair means you have access to safe, reliable heat when winter starts. A poorly maintained furnace is more expensive to operate, more prone to breakdowns, and more dangerous for your family. Below are some of the recommended items that come with an annual furnace maintenance service.

Regular Filter Replacement

In Portland, you might need to change your air filter every few months, depending on local air quality and your filter and furnace size. Larger units might need more frequent filters, though these units may also simply use larger filters. Let your HVAC maintenance company handle the details.

Cleaning and Inspecting Components

A dirty igniter might mean you have no heat, while dirt and debris in your combustion chamber can be a fire risk. Have your system professionally cleaned at least once a year to minimize your risks.

Professional Annual Inspections

Annual inspections help you avoid unexpected furnace repair calls. Your Four Seasons Heating and Air technician will give you a snapshot of your system's current condition and any repairs that might be on the horizon.

Lubrication of Moving Parts

If it moves, it needs the occasional drop of oil or grease. During a maintenance visit, our techs check and lubricate all the moving parts to avoid mechanical failures.

Energy Efficiency Tips

With the right system and use, you can heat your home affordably. There are basic home repairs and tricks you can use to keep heating costs down while staying warm this winter. Below are some of the most effective ways to get your home to the temperature you want without unchecked costs.

Programmable Thermostats

Don't heat your home to comfortable temperatures when no one is home. Programmable thermostats let you turn the heat down when you go to work and automatically turn it back up when you're due home in the evening.

Adequate Insulation

Drafts mean you're losing already heated air. Make sure to check for heat loss, and seal up any leaks.

Duct Sealing

Some areas of your home are more insulated than others. If your ducts leak into your unfinished basement or attic, that means you lose a lot of heat. Sealing your ducts can help dramatically reduce the cost of heating and the wear and tear on your furnace.

Furnace Tune-Ups

An annual furnace tune-up helps delay the need for major repairs. Think of it like oil changes for your car. If you don't get them on time, expect to have more frequent malfunctions and to need more expensive repairs.

When to Upgrade Your Furnace

If your furnace is older, you might be thinking about installing a new one. Here are some tips to help.

Signs It's Time to Upgrade

If your furnace doesn't effectively heat your home, even when it's working properly, it might be time to upgrade. Any time the repair cost exceeds 50% of the replacement cost, it's also time to seriously consider buying a newer furnace.

Choosing the Right Furnace Size

Bigger doesn't always mean better when it comes to furnace size. Have a professional run the load calculations to determine the right size for your home. Too small and the furnace won't produce enough heat. Too big and it will cost too much to run. Find the optimal size.

Energy Star Ratings

Opt for the highest-rated furnace that makes sense for your budget. Better Energy Star ratings mean lower monthly heating costs.

Smart and High-Efficiency Furnace Options

High-efficiency furnaces and smart options turn on when needed and shut off when not, helping to preserve power. Some high-efficiency options even have low and high power modes to preserve energy when you only need a little bit of heat.

When you need help with a furnace install, call Four Seasons Heating and Air Conditioning.

Our team, comprised entirely of NATE-certified HVAC specialists, excels in furnace repair, maintenance, and installation. We're committed to ensuring your complete satisfaction with our services!

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