Common Furnace Problems Every New Homeowner Should Be Aware Of
Have you recently bought a new home with a gas furnace? Having a furnace in your home is great since it allows you to heat your house effectively while keeping your heating costs fairly low. The only issue is that gas furnaces are quite complex, which means there are a variety of things that can go wrong and prevent your furnace from running, reduce its effectiveness or even make it unsafe to use. In this article, we’ll explore the most common issues a furnace can have so you know what to watch out for and when you need to call in the help of a certified HVAC company.
1. Dirty or Worn-Out Flame Sensor
The flame sensor is often one of the first components to wear out in a gas furnace, and that’s because it sits right next to the burners and is constantly exposed to extreme heat when the furnace is running. The purpose of a flame sensor is to reduce the risk of a fire or explosion that can potentially occur if gas continues flowing when the burners are lit. A small electrical current flows through the sensor and interacts with the flames coming off the burners. This enables the sensor to know whether or not the burners are lit.
If the flame sensor is worn out, it will prevent your furnace from heating since the gas valve will close within a few seconds of opening due to the sensor not detecting the burner flames. That means the burners will light and then go out almost immediately. This same issue can also happen if the flame sensor is dirty. A dirty flame sensor prevents the current flowing through it from interacting with and detecting the burner flames.
2. Worn-Out Electronic Igniter
While older furnaces had a pilot light that detected the flames from the burners, virtually every modern furnace instead uses an electronic igniter. The reason that manufacturers moved away from pilot lights is to improve energy efficiency since a pilot light needs to constantly burn a small amount of gas to keep its flame lit. While electronic igniters help with efficiency, they can also end up wearing out and making it so that the furnace never lights.
The most common type of electronic igniter used nowadays is a hot-surface igniter. It gets hot instantly, causing the heat radiating off of it to ignite the gas flowing to the burners. The fact that the igniter gets so hot means it almost always gets damaged over time to the point where it gives out. When this happens, the only option to get your furnace working again is to install a new igniter.
3. Damaged or Malfunctioning Pressure Switch
Any furnace installed in the US since 1992 is a draft-induced unit. This means it has a draft inducer fan that draws the combustion fumes upward so that they continuously flow through the heat exchanger and eventually get vented outside. The purpose of the draft inducer is to ensure that the furnace heats efficiently and that the fumes always flow directly outside.
When your furnace turns on, the first thing that you hear is the noise of the draft inducer running. As the inducer draws air upward, it creates negative pressure that activates the pressure switch. Once the pressure switch activates, the furnace’s control board then opens the gas valve. If the pressure switch is damaged or stops working, gas won’t ever start flowing to the burners and thus the furnace can’t turn on when it should. The same thing happens if the inducer doesn’t work or isn’t working well enough to activate the pressure switch.
If your furnace won’t turn on, it’s quite easy to determine if the issue is due to the electronic igniter, the pressure switch or the flame sensor based on what happens when the furnace tries to start. If you can briefly hear gas flowing but the furnace doesn’t light, the igniter is usually the culprit. If the burners turn off almost immediately after lighting, the issue lies with the flame sensor. If you hear the draft inducer running and nothing else happens, it means there’s an issue with the pressure switch.
4. Dirty Burners
One reason you should always have a gas furnace serviced every year is to ensure that the burners are clean. The main issue when the burners are dirty is that it can sometimes prevent the furnace from burning cleanly. If the gas doesn’t burn cleanly, it will produce yellow or orange flames that give off far less heat and result in the air the furnace puts out not being nearly as hot as it should be. The bigger concern in this situation is that carbon monoxide often gets produced when natural gas doesn’t burn cleanly and only partially combusts. This is why it’s a good idea to periodically check your furnace throughout the winter to see what color the flames are. Bright blue flames indicate the furnace is burning cleanly. If the flames are flickering and are orange or yellow, it means you should call to have your furnace inspected and serviced as soon as possible.
5. Overheating
One issue that commonly occurs if the furnace isn’t receiving sufficient airflow is that it will end up overheating. This can happen due to the furnace filter being too dirty, the blower not working properly or because of an issue with your ductwork. Although a furnace has a safety switch that will instantly cause it to shut off if it overheats, repeated overheating can still result in major damage and greatly shorten the life of your furnace. If your furnace constantly overheats, your house will also never be as warm as you want due to the furnace shutting off midway through its heating cycle. If you notice that your furnace shut off before your thermostat registered the right temperature, you should change the air filter to see if this fixes the issue. If it doesn’t, you’ll need to have a technician perform an inspection to determine if your furnace is overheating or has some other issue, like a malfunctioning flame sensor or pressure switch.
6. Cracked Heat Exchanger
While this problem isn’t all that common, it’s still worth mentioning since it results in a furnace no longer being safe to use due to the risk of carbon monoxide exposure. A heat exchanger is what allows a gas furnace to heat effectively and safely. That’s because it captures most of the heat produced by the burners and transfers it to the air flowing through the furnace. At the same time, the heat exchanger prevents the combustion fumes from mixing with the hot air the furnace produces. Under normal conditions, the hot fumes get drawn out of the combustion chamber. The fumes then flow through the heat exchanger tubes before eventually rising through the flue where they then get safely vented outside.
If there is a crack in the heat exchanger, some of the fumes can leak out through the crack where they will then mix with the hot air and get blown throughout the house. If your furnace also isn’t burning cleanly, you can then end up with a perfect storm that results in carbon monoxide blowing out of the vents into every room. This is one reason why annual inspections and maintenance are so important since these services ensure that your heat exchanger is still in good shape and that your furnace burns cleanly.
Our Experts Can Help
If you need to have your furnace inspected, serviced or repaired, you can trust the experts at Brennan Heating & Air Conditioning. We’ve been serving Seattle and the Puget Sound area since 1987 and have what it takes to help you overcome any issues with your heating, air conditioning, plumbing or electrical system. We work on all makes and models of HVAC equipment and also offer reliable installation and replacement services. If you’re experiencing any issues with the furnace in your home, give us a call and we’ll get it working properly again as soon as possible with out heating repair services.
