October 18, 2023
Is It Normal for Your Furnace to Smell Like it’s Burning?
Have you ever noticed a burning smell coming from your heating system when you first turn it on? If so, your first thought was probably what caused the burning smell and whether it is something you need to worry about. The truth is that this type of burning smell is quite common but can also be a sign of a potentially serious issue. Today, we’ll explore the reasons your home’s heating system smells like it’s burning so that you can know when it’s normal and when it indicates a problem.
Dust and Debris
Furnaces and electric heaters like baseboard heaters often produce a burning smell when you first turn them on after sitting unused for a long time. This typically happens when you first use your heating in the fall or winter. Dust, cobwebs, and other debris tend to collect inside a furnace or electric heater when it sits idle during the warmer months. It then burns off when the heating system is turned back on. You’re more likely to notice the smell when you don’t have your heating system serviced and cleaned.
If you have a central heating system with a furnace, you’ll often notice this smell not only when standing next to the furnace but also wafting out of some or all of the vents in the home. When dust coats electric resistance heating coils in an electric baseboard heater or electric furnace, it will burn off more slowly and produce a stronger smell that lingers in the air for longer. If you have baseboard heaters, the smell could also indicate that a piece of paper or some other foreign object got dropped inside of the unit, which will need to be addressed to prevent a possible fire.
While this type of burning smell is common, the only time your heating should ever smell like it’s burning is when you haven’t used it in some time. The smell should also dissipate fairly quickly once all of the dust has burned away. In most cases, the smell will start to fade and completely go away within 15 to 30 minutes. If you continue to notice the smell for a longer time or your heating smells like it’s burning when you’ve been using it regularly, shut the unit off and get it inspected for all of the following issues.
Damaged wires or loose electrical connections in a central heating system or any type of electric heating can cause the electrical current to spark or arc, which can cause the insulation on the wiring to start melting or even catch fire. If the circuit that your heating system is on gets overloaded with too much current flowing through it, the wires can also quickly heat and melt the insulation. These issues will lead to a strong burning smell and an acrid odor like the smell of burning plastic.
This is an extremely serious issue that requires immediate attention and is not something you can ignore. As such, you should always shut your heating off until you can have a professional perform a full inspection. You should also flip the circuit breaker off for your heating system or electric heating units just to be safe. Electrical issues like these are a major fire hazard, and electrical problems can also cause severe damage such as frying the control board on your furnace or burning out the blower motor.
A furnace or furnace blower can overheat for a variety of reasons. All modern furnaces and central heating systems have a safety mechanism known as a high-temperature limit switch and sensors that constantly measure the temperature inside the furnace and the temperature of the blower motor. The limit switch is designed to automatically shut the heating system down if the furnace or the blower ever starts overheating, which is important for preventing damage or anything catching fire.
Limit switches can wear out or malfunction, which means they are failing to shut the system off when it overheats. Even if the limit switch does work as it should, you could still notice a burning odor just before or just after the system shuts down. If your heating system ever shuts off before it should and you notice a burning smell, the likelihood is that the system overheated.
Furnaces most commonly overheat either because the HVAC air filter is clogged or because too many vents in the home are closed, clogged, or obstructed. A clogged filter will prevent the blower from pulling sufficient cool air into the furnace. This means that the furnace won’t be able to dissipate all of the heat it produces, potentially causing the furnace to quickly get hotter and start overheating. If lots of supply vents are closed, clogged, or obstructed, all of the hot air won’t be able to flow out quickly enough to prevent the system from overheating. A clogged air filter or lots of dust on the squirrel cage around the blower can also lead to the blower motor overheating because it has to work so much harder to move air through the system.
A flame rollout is when some issue causes the flames from the furnace burners to “roll out” or escape the combustion chamber. This issue can occur any time the combustion fumes can’t flow out of the chamber through the heat exchanger and into the exhaust flue, which typically happens because either the flue or the heat exchanger tubes are clogged.
A flame rollout can also occur because of issues with the gas lines or gas valve or because the burners are overly dirty or clogged with debris. If the burners are clogged or dirty, the gas won’t burn cleanly and more exhaust fumes will be produced. When the combustion chamber fills with fumes, the burner flames will not be able to get the oxygen they need.
The combustion chamber is designed to handle all of the heat and flames with no issue, but a rollout can lead to the flames reaching places that aren’t meant to handle extreme heat. This can singe the exterior of the furnace or heat the metal to where it starts smoking and producing a burning smell. The flames can also damage the electrical components to where they start smoking.
Flame rollouts tend to be a more common issue with older furnaces. This is because most newer furnaces have a flame rollout switch that will automatically shut the entire heating system down if a rollout ever occurs or if the combustion chamber starts to fill with fumes. The flame rollout switch is another essential safety mechanism since rollouts can cause extensive damage or even cause the furnace or any nearby items to catch fire. If you notice any visible singeing on the exterior of your furnace, it should be inspected as soon as possible.
With more than 45 years of experience, Scott-Lee Heating Company is the most trusted choice for all of your residential or commercial heating needs in the St. Louis area. We specialize in heating inspections, repairs, maintenance, and installations and offer expert air conditioning services. If your heating smells like it’s burning or has any other issues, give us a call and we’ll make sure everything works safely and effectively.