Has your heating system suddenly started to produce a strong smell like it’s burning? Noticing a burning odor coming from your furnace and heating system can be quite frightening and may make you think of the worst.
A burning smell isn’t always a cause for alarm, but it’s also not something you should ignore. In this article, we’ll explain the various issues that can cause your heating system to produce a burning smell and what to do about each one.
Dust Build-Up
One thing you should understand is that a burning smell isn’t always a sign of a problem. When the cold weather arrives and you turn your heating system back on for the first time, it’s completely normal for your furnace to temporarily produce a burning smell. This smell will be strongest if you’re standing near the furnace, but you’ll likely also notice it wafting out of all of the vents.
When a furnace sits unused for months, lots of dust can accumulate on the burners and inside the combustion chamber. Once you finally turn the furnace back on, the dust will start to burn away and produce a noticeable burning smell. The smell may be even more pronounced if you have pets since lots of pet hair and dander can easily get trapped inside your furnace when you don’t use it for a long time.
This burning smell normally isn’t a cause for concern and should quickly dissipate within 10 to 15 minutes. The only time you need to worry in this situation is if the smell doesn’t go away. If the smell continues to linger for some time or gets stronger, you should shut your heating system back off and contact us for an inspection.
Debris or Foreign Object in Your Ductwork
The air produced by a gas furnace is typically around 120-140 degrees. While the air generally isn’t hot enough to cause things to combust, it can still result in a strong burning smell if there is something trapped inside one of your air vents. If the inside of the vent is full of lots of dust, the hot air can also make it smell like it’s burning.
In this situation, the smell will typically be confined to one room or area of the home. If you can pinpoint where the smell is coming from, you should take the cover off of that vent and look inside for any objects or debris. If there is anything inside of the vent and you remove it, the smell should also quickly go away.
Overheating
Modern furnaces have a temperature-limit switch that is designed to shut the heating system off if the heat exchanger ever gets too hot and the furnace starts overheating. If you notice a burning smell and your furnace shuts off before your home has reached the correct temperature, it’s a fairly sure sign that your furnace is overheating.
Overheating can be a serious issue since it can cause the wires in the furnace to melt or potentially even lead to the furnace catching fire. If the heat exchanger gets too hot, it can also crack. This can be an even more serious problem since a cracked heat exchanger will allow carbon monoxide to escape and leak out into your home. These issues are why you should shut your heating off at the thermostat and take a few steps before trying to run it again if you suspect your furnace is overheating.
Overheating is normally caused by airflow issues. If there isn’t enough cool air constantly flowing through the furnace and over the heat exchanger, the temperature will quickly start to increase. The main reasons that a furnace won’t have proper airflow are because the air filter is too dirty or some of the vents are closed, clogged, or obstructed. As such, you should always check the air filter and replace it if it looks dirty any time you suspect your furnace overheated.
You’ll also want to go around your house and make sure that all of the supply and return air vents are fully open. You should also check that the vent covers aren’t clogged with debris and that nothing is blocking the airflow coming out of the vents. If more than a few supply vents aren’t open, the heating system won’t be able to properly circulate all of the hot air coming out of the furnace. This leads to the heat quickly building up and can cause the furnace to overheat.
After checking the air filter and vents, you can then try turning your furnace back on. If it runs properly and completes a full heating cycle without shutting off prematurely and the burning smell doesn’t return, it should be fine to leave it running. If it shuts off before fully heating your house or you notice the burning smell again, you should shut it back off and leave it off until you can have a professional inspection performed.
Electrical Issues
Electrical issues like a loose connection or frayed wire can also lead to a heating system producing a strong, acrid burning odor similar to the smell of burning plastic. When an electrical issue is present, the current can arc or a wire can short circuit.
This can cause the wire to heat up to where the shielding around it starts melting, smoking and producing a strong burning smell. Electrical issues can also cause the blower motor to overheat and smell like it is burning. If the blower motor overheats, it could burn out and force you to replace it.
An acrid smell like burning plastic is a sign that your furnace has a more serious problem, so it is definitely not something you should ignore. The reason is that electrical issues can be a serious fire hazard, which is why you should immediately shut off your furnace in this situation.
Flame Rollout
A flame rollout is also a serious issue and is when the burner flames suddenly grow much bigger and start “rolling out” or escaping the combustion chamber. Flames require oxygen to continue burning. If the flames aren’t receiving enough oxygen, they’ll quickly get much bigger as they grow out in search of oxygen. This can lead to the flames reaching parts of the furnace that aren’t designed to be directly exposed to extreme heat, which can cause wires to melt or components to start smoking. The flames can also start singeing the sides of the furnace and cause the metal to get hot enough that it smells like it’s burning. A flame rollout can even catch the furnace or nearby objects on fire.
Most modern furnaces have a flame rollout switch that will instantly trigger an automatic shutdown if a flame rollout occurs. If your furnace does have flame rollout issues, you will normally see signs of singeing. In this case, you definitely want to leave the furnace shut off until a technician can inspect the burners, heat exchanger and exhaust vent.
If the heat exchanger or exhaust vent is clogged or the combustion fumes aren’t being vented outside properly, the fumes will start building up inside the furnace. This prevents the flames from receiving sufficient oxygen and can lead to a rollout.
If your furnace smells like it’s burning and you need to have it inspected, you can turn to the experts at Laury Heating Cooling & Plumbing for help. We service all makes and models of furnaces as well as heat pumps, air conditioners and mini-splits. Our team can help if you need heating installation or replacement or cooling, as well as any residential plumbing service in South Jersey. To schedule a heating inspection or any other service, give us a call today.
