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The furnace is a wonderful invention that has become requisite to nearly all homes in the United States during the winter months. Still, homeowners often fret about when they own this appliance if it's supposed to make the sometimes loud and boisterous noises they hear. We've done the research to tell you what you can expect from your furnace.
It's quite normal for a furnace to make noise. Some common noises for a furnace to create during its run cycles are hums, chirps, and rattles.
However, there are some instances when noise is not normal for a furnace, which could indicate an issue. When you notice a noise that seems unusual for your furnace, you should always call a professional to service the unit.
So now we've explained that some sounds are normal for this appliance, but you may have other questions. You may especially want more details about what noises are considered standard and what noises could be caused by a mechanical problem. Keep reading to learn more.
How A Furnace Works
To understand the different noises a furnace creates and determine whether they are standard or harmful, it's helpful to understand the unit's design and how it operates.
Gas furnaces are fueled by, you guessed it, natural gas. The fuel must enter the unit by a pipe connected to the fuel source, either underground or on the exterior of the home. There is a burner in the unit, and when the fuel enters, it is lighted.
The cold air in your home is cycled through the furnace. When it enters, it is heated in the heat exchanger. This warm air is then forced throughout the home by the blower, and the exhaust is released through the vent to the exhaust pipe.
This process continues until the internal temperature in the home reaches the selected temperature on the thermostat, and then the furnace cycles off.
The electric furnace has a simpler design than its gas counterpart. The electric furnace has no fuel source and fewer moving parts, which means a much quieter unit. Most of the sounds we will discuss in this article will be heard from gas furnaces.
Inside the electric furnace, you can find heating elements such as coiled wires, which are warmed by electrically charged particles. Cool air from the home is pulled inside the furnace and warmed in the heat exchanger. Once this air has been warmed, it is forced throughout the home by the blower.
What Does A Normal Furnace Sound Like?
Furnaces, especially the gas types, are notorious for being noisy, but there are the sounds of a healthy furnace and a not-so-healthy furnace.
Single Click and Hum
As discussed earlier, gas furnaces contain a burner, and when the gas enters the burner chamber, it is lighted. If you hear a single click coming from your furnace followed by a hum, this is normal. It's the sound of your burner lighting and the unit cycling on.
Subtle, or dull, chirps are usually no cause for alarm. As the mechanics within a gas furnace are moving, this can cause a small amount of friction. The chirps are simply the sound of these mechanics in motion.
A rattle that lasts for a short time is a typical noise for your furnace. This is usually heard when the furnace is cycling off. All of the mechanics inside the furnace have been hot and in motion, and these moving parts may rattle as they come to rest and cool.
What Does A Bad Furnace Sound Like?
There are also a few sounds that may be signaling an issue within the unit.
There are many moving parts within a gas furnace, including the mechanics of the motor and blower wheel. If these parts begin to wear or fail, you may begin hearing a high-pitched screech or scrape. You may be able to quickly conclude that the mechanics are scraping one against another.
It's important to note that this can sound like a bird chirping, but it will be much more grating and high-pitched than the "dull chirps" that are heard in a typical functioning furnace.
A squeal is a sound that most likely is signaling an issue with the blower motor belt. This is also a sound and problem that can be experienced with an electric furnace. This can be easily fixed by adding oil in some cases, but the belt or motor may need to be replaced in others.
As detailed above, the single click of a furnace is just a signal that the furnace burner is lighting, but if you hear continuous clicking from the furnace, this most likely means that the burner is unable to light.
There are several reasons this may be. There may be an incorrect air and fuel composition, a malfunctioning flame sensor, or a malfunctioning gas valve. In all cases, the burner would be incapable of lighting.
Of course, a loud boom is alarming, but the issue could actually be a relatively small one - dirt. When burners within a furnace get dirty, this impedes lighting. Gas will build up within the burner chamber and essentially create a small explosion.
While a furnace is designed to cycle off when there is a serious issue to prevent overheating and explosions, it's important for you to know that excessive dirt on the burners can cause carbon monoxide leaks.
How Do You Fix A Noisy Furnace?
There is a list of things that can be done by a homeowner to both prevent, and at times, fix a noisy furnace.
- Replace the air filter every three months.
- Clean burners and flame sensor once per year.
- Oil motor blower and inducer fans once per year.
- Inspect electrical wirings and controls for corrosion once per year.
- Test thermostat for proper operation with furnace once per year.
- Check for debris and clean air registers and ductwork once per year.
- All of this should be done in conjunction with yearly professional servicing.
When you notice an unusual noise that you believe could be causing a serious issue, we always suggest consulting with a professional. Furnaces, especially of the gas type, can be dangerous when improperly managed or fixed. The risks could include overheating of the unit, explosion, or carbon monoxide poisoning.
When bringing in an HVAC professional to fix your noisy furnace, you can be sure that the issue will be fixed correctly and that the unit will be safe for your family.
Now that we've answered your initial question, we thought we'd cover some other frequent questions about furnaces.
Why Is My New Furnace So Loud?
If you notice that a furnace you have just purchased is especially loud, it does not necessarily mean that it is malfunctioning. It could simply mean that you are not used to the noise of that specific unit. However, if you notice that some of the noises are unusual or disturbing, you should probably have the unit serviced to be sure.
How Long Does A Home Furnace Normally Last?
When a home furnace is maintained correctly, one can reasonably expect it to function for 15 to 20 years. If your furnace is nearing this timestamp, you could begin shopping around to replace the unit when you're ready.
However, you may have even more time than this if your furnace is of good quality and has been meticulously cared for, even up to 30 years.
Though the noises that come from a furnace can disturb your peace, they're not always something to be worried about. Many times, the sounds coming from a furnace are routine, but if you hear scraping, squealing, continuous clicking, or booms, that's when we highly suggest obtaining a professional to take a look at the unit.
Always remember to keep your furnace working properly and your family safe with proper maintenance and regular servicing. Stay warm!
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