No furnace is completely silent, but there can be certain times when the noises produced by your unit become impossible to put up with.
Unusual sounds coming from a furnace can be indications of various problems within the system. Gas pressure issues, dirty gas burners, a damaged belt, restricted airflow, issues with the capacitor and fan – all these things can make your furnace noisier.
Why Is My Furnace So Noisy?
Practically any mechanical device, especially one with a fan, is going to make some noise. When it comes to furnaces, the noise level is usually quite low.
However, if you have never had such a heating unit before, it might come to you as a surprise that these systems are not silent. The only reason why you would be noticing these sounds is that they weren’t there before and as soon as you get used to the new noise, it won’t bring any discomfort.
Related: How Much Does It Cost To Move a Furnace and Water Heater?
What does a normal furnace sound like?
The unit is going to make a noise whenever it starts up and the heating cycle begins. You are going to hear a pop or a click when the furnace fires up and then – dull humming.
Some units are going to be quieter than the others, but all-in-all the sounds of a correctly operating furnace shouldn’t become an inconvenience to you.
What Does a Bad Furnace Sound Like?
You might be asking yourself ‘when should I worry about my furnace noise?’.
As a rule of thumb, any unusual sound can become a cause for concern. Those might indicate that there is something wrong with your furnace.
A loud boom can be caused by a small ‘explosion’ that occurs when there is an ignition delay. When the gas burners do not ignite on time, the gas has a few spare seconds to build up in the chamber.
This happens either because the gas burners are dirty or because there is a gas pressure issue. In any case, a professional should take care of such an issue.
You might also hear popping as soon as you turn the furnace on. This happens when heated air hits the cold ducts.
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A high-pitched squealing noise
You’ll hear a shrieking noise if there is a problem with the motor. It might be because of a damaged or loosen belt – this is a relatively easy fix.
Unfortunately, squealing sounds can be indicators of a more serious problem with the actual motor.
Rambling and rattling noises
This happens when one of the parts within the heating system becomes loose. The vibration caused by the components is what makes a rattling noise.
If the rumbling continues even when the furnace finishes a cycle, it might be because fuel is continuing to burn in the chamber (even though the burners had already shut down).
If you hear a whistle coming from the furnace, then it looks like the airflow is restricted.
Related: How To Increase Airflow in Ductwork
In the majority of cases, all you would have to do is change the filter. At times, the airflow can also be restricted by dirt in the grilles and air handler.
If you hear a low hum, then there is nothing to worry about. But if it has become louder, then there might be an issue with the capacitor or blower fan.
Furnace Sounds Like a Dryer
You might hear a thump or vibration that will make your furnace sound like a dryer. The chances are high that, in such a case, the blower wheel is imbalanced.
Furnace Sounds Like a Train Whistle
This high-pitched noise might also remind you of an airplane.
A leak in the ductwork might be causing such a sound or the blower motor bearings that have become worn out.
How Do You Fix a Noisy Furnace?
As you might have already figured out from all the issues mentioned above, it is better to call a professional whenever you hear your furnace make a strange noise.
Usually, these annoying sounds indicate serious problems with the furnace’s components, so leaving that to an expert might be the best decision.
However, there are a few simple things that you can do to try to get rid of the noise problem on your own.
Check the Ductwork
If you hear a banging or popping sound coming from a certain place in the ductwork, then you can attempt strengthening this weak spot.
For example, you can screw a piece of metal that is slightly thicker than the duct across and onto the existing metal.
Related: How Hard Is To Replace Ductwork?
If you hear a whistling sound, then, once again, try to figure out where it’s coming from. Your ductwork can have a few gaps or you might find a hole in the place where the ducts connect to the furnace.
In any case, use foil tape to seal all these leaks.
Fact: up to 30% of air gets lost in the ductwork due to holes, leaks, and poorly connected ducts.
Finally, whistling can indicate that your ducts are simply too small. If you have a powerful furnace, it might require a greater airflow that the ducts are not able to let through.
Replace the Filter
The easiest way to fix a whistling noise problem is to simply replace a dirty filter with a new one.
Remove the filter to find out if this is the thing that is causing the sound. If yes, then remove the clogged component and insert a brand-new filter.
Related: Why Does My Furnace Filter Get Dirty So Quickly
You should replace your filters at least once every 90 days, but sometimes it has to be done a bit more often.
Check Ignition Malfunction
You are not going to fix the problem if you follow the steps below, but you are at least going to have an understanding of what’s going on.
- Try seeing into the furnace doors during the furnace start-up.
- If you can’t really see anything, then listen (you might hear a bang) and watch to see if the doors are shaking.
- If you have spotted any extra flame, a banging sound, or the doors were shaking, then there is a serious issue with the gas ignition.
- This problem can potentially be dangerous, so call your HVAC expert right away.
Hint: newer furnaces shouldn’t have such a problem at all as they feature a ‘roll-out sensor’ that prevents such an issue from occurring in the first place.
How to Quiet a Noisy Furnace Blower?
Here are the things that you can do to reduce the noise coming from a furnace blower.
Build sound insulation
Most of the noise is coming from the blower intake, so you can use melamine foam to insulate this part of the system.
You would have to use a steel wire to secure the foam in place, but all the efforts might be worth it.
Consider getting a variable-speed blower
Such blowers are practically silent (unlike single-speed blowers). As a bonus, variable-speed models will help you reduce your heating bills and will help make sure that your house is heated more efficiently.
Add return air ducts
You can easily check if the blower has insufficient return air. Simply open the air filter door, and if that had made the whistling noise go away, then you should definitely consider adding a few return air ducts.
You would have to invite a professional to help you with that.
Adjust the fan speed
This is a simple trick that can do wonders.
Try decreasing the fan speed and then check the airflow. If you feel comfortable in your house even with a low-speed fan, then leave it that way.
Replace the loose parts
Loose fins on the blower or a loose belt can be causing a lot of furnace noise problems. It might be much cheaper to replace the part than to continue putting up with the noise.