Despite the fact that they produce a lot of heat, furnaces really shouldn’t ever produce any burning odors or other unusual smells. There is only one time when it is normal for your furnace to smell like it’s burning, and this is when you first turn it on after it has sat unused for a long time. If you notice a burning smell coming from your furnace any other time, then you will want to have your furnace inspected as soon as possible so that whatever issue it is experiencing can be repaired.
Once the furnace turns back on, it is normal to notice a burning smell for a few minutes or even as long as an hour or two. If the smell goes away after a while, you have nothing to worry about, as all you smell is the dust inside the unit burning off.
If the smell doesn’t go away, you will want to shut the furnace off until you can have it inspected, or else you may run the risk of causing serious damage to either the furnace or the blower fan. The same is also true if you notice a burning smell at any time other than when you turn the furnace on for the first time each year.
Overheating Furnace/Blower Fan
One of the main reasons that a heating system will produce a burning smell is because either the furnace or the blower fan is overheating. When either unit overheats, the wiring can melt and produce a smell similar to burning plastic. An overheating blower motor can also produce a burning smell as it can get so hot that it starts to smoke slightly.
Overheating can occur for various reasons, but the most common cause is a dirty air filter. As a result, the very first thing you’ll want to do if you ever notice a burning smell checks the filter’s condition. If the filter looks black or is covered in a thick layer of debris, you should immediately replace it to see if this fixes the issue. You can also avoid this problem by simply ensuring that you replace your air filter once every four to 12 weeks.
If the air filter is clogged with dust and debris, it drastically restricts how much air can flow. This means that the blower fan will have to work much harder to draw air into the furnace and circulate it throughout the building, which can quickly overload the blower motor and cause it to overheat.
A clogged air filter will also limit the amount of cold air in the furnace. Unfortunately, this results in much of the heat that the furnace creates getting trapped inside the unit, which can lead to the furnace overheating itself.
Furnace Flame Rollout
Another reason that furnaces can produce a burning smell is due to a flame rollout. A flame rollout is when the flames escape or “roll out” of the combustion chamber. This can result in the flames reaching parts of the furnace that aren’t designed to withstand heat. A flame rollout can also singe the furnace’s exterior and can even produce enough heat to start nearby materials on fire potentially. As a result, this is an issue that you will want to have taken care of immediately.
A flame rollout occurs when the combustion fumes get trapped inside the furnace instead of flowing out through the exhaust flue. These fumes will quickly fill the combustion chamber and starve the flames of oxygen. As a result, the flames will quickly grow larger and escape the combustion chamber in search of oxygen.
Flame rollouts usually occur for one of three reasons. The first is that the exhaust flue is blocked or not working properly, which means the combustion fumes can’t escape. Flame rollouts can also occur due to soot blocking the outlets where the fumes flow out of the combustion chamber into the heat exchanger. The other possible cause is that the furnace’s heat exchanger is cracked. No matter what the cause, a flame rollout is an extremely serious problem as it means that the carbon monoxide and other dangerous fumes aren’t being vented outside as they should be.
If you have a burning smell coming from your furnace or are experiencing any other issues, Northwest HVAC Heating & Cooling is ready to help. Our team repairs and maintains all types and brands of furnaces, and we also specialize in furnace installation. If you need any cooling or indoor air quality services in the Vancouver area, we can help with that as well. Give us a call today to schedule a furnace inspection or any other HVAC service.