Furnaces require quite a bit of regular maintenance to ensure that they can heat safely and effectively. Proper maintenance also keeps the furnace working efficiently so that it doesn’t use more energy than necessary. This can make a big difference in the furnace’s repair needs and how long it lasts. When it comes to maintaining a furnace, the first thing to understand is that the most important tasks should be performed by a certified HVAC technician. The only thing you should do yourself is change the furnace filter. This is something you should do every one to three months. In this article, we’ll look at all the other tasks that are involved in maintaining a furnace and explain the importance of each one.

Cleaning and Testing the Flame Sensor

The flame sensor is one of the most important safety components in a gas furnace. Its purpose is to prevent the risk of an explosion that could occur if the furnace’s gas valve were to stay open when the burners weren’t lit. The way it works is that a small electrical current flows through the current and interacts with the flames produced by the burners to ensure they light immediately and stay lit throughout the heating cycle. If the sensor has gone bad or is too dirty to detect the flames, it will send a signal to the control board within a few seconds so that the gas valve closes, and the burners go out. This is why it’s important to clean and test the flame sensor, or else you may encounter issues where your furnace suddenly won’t stay lit for more than a few seconds.

Testing Other Safety Switches and Sensors

In addition to the flame sensor, modern furnaces have several other sensors and switches. Each of these components is also designed to ensure safe operation and help to avoid the risk of a fire and other potential hazards. As such, part of maintaining a furnace is for a technician to test each one to ensure they work so that you can prevent any hazards and ensure your furnace runs when needed.

One component that is essential both for safety and ensuring the furnace runs when it should is the pressure switch. Since 1992, the United States has required that all new furnaces be draft-induced. This means they have a draft inducer fan that draws air upward to ensure that the combustion fumes flow into the exhaust flue and are safely vented outside. Having the draft inducer fail can be a safety hazard since it creates a potential for the fumes to escape and leak out into your home. This is where the pressure switch comes in since it will only allow the furnace burners to ignite if the inducer is running and creates sufficient negative pressure to activate the switch. If the switch is broken or the inducer isn’t working, the gas valve on the furnace won’t ever open and the furnace won’t turn on.

Another important safety component is the temperature-limit switch, which serves two different purposes. You’ve probably noticed that the blower in your heating system doesn’t turn on and start circulating air for around 30 to 60 seconds after the furnace lights. The reason for this is that the limit switch senses the temperature of the furnace’s heat exchanger and won’t signal the blower to run until the exchanger is sufficiently hot. This is just to ensure that the exchanger gets hot enough for the furnace to heat effectively. The other purpose of the limit switch is to prevent damage and the potential of a fire that can result if the furnace overheats. That means if the heat exchanger ever rises above a certain temperature, the limit switch will immediately signal the gas valve to close and the furnace to shut down.

One final safety feature you’ll find in many newer furnaces is a flame rollout sensor. A flame rollout is when there is an issue that allows the burner flames to escape the combustion chamber. This can be extremely dangerous since it can potentially catch nearby items on fire, and it also creates a risk of damaging various components in the furnace.

Cleaning the Furnace Burners

Cleaning the burners on a gas furnace is important both for safety reasons and to ensure the furnace heats effectively. If the burners are dirty, you’ll sometimes end up with an issue where the gas flowing out of them doesn’t fully combust. When this happens, it results in the flames not giving off nearly as much heat and thus makes the furnace work much less effectively. The bigger issue is that incomplete combustion results in the gas not burning cleanly and potentially producing carbon monoxide. Under normal circumstances where the gas fully combusts, carbon monoxide is never a worry since natural gas only produces carbon dioxide and water vapor when it burns cleanly.

Cleaning and Testing the Blower

Another thing a technician will do is clean all the dust from the blower and test it to make sure it can still circulate the proper volume of air. If the blower is too dirty or not working properly, you’ll encounter various issues, such as your furnace not putting out sufficient heat and using too much energy. A bigger issue is that you can easily end up with your furnace frequently overheating because there is not enough cool air flowing over the heat exchanger.

Inspecting and Testing the Exhaust Flue

Even if the draft inducer and pressure switch are working as they should, there is still a risk of combustion fumes leaking out into your house if there are any issues with the furnace’s exhaust flue. That’s why a technician will always fully inspect the flue to make sure it is not damaged and was installed and designed correctly.

Inspecting the Heat Exchanger

One final task that’s extremely important is for a technician to fully inspect the furnace’s heat exchanger, which is what keeps the combustion fumes separated from the air flowing through the furnace so that the furnace can heat safely. A heat exchanger consists of several metal tubes that run between the combustion chamber and the exhaust flue. The tubes are welded on each end to create an airtight seal to ensure no fumes can escape and mix with the hot air the furnace produces. Over time, the weld joints can end up cracking or the tubes can develop holes due to the furnace overheating or simply because of aging and normal wear and tear. This is a serious issue since it allows the fumes to get into your ductwork, creating a potential for carbon monoxide to get pumped throughout the house.

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