‘Twas the night before Christmas, and all through the house, not a creature was stirring…except the noisy furnace!

Anyone who’s had their quiet evening at home interrupted by a mysterious rumble, rattle, or squeak and asked, “what was that?” knows furnaces can make some pretty interesting noises. And with good reason; after all, furnaces are pretty hefty machines, doing a big job, and they’re bound to make a bit of noise now and then—even tucked away in the basement.

But if you’re hearing continuous or decidedly unusual noises emanating from your furnace this holiday, your best bet lies in isolating any potentially problematic parts so you (or your HVAC professional) can help you enjoy a truly silent night.

Possible Causes of a Noisy Furnace

Your furnace is big. It has both moving parts, such as your blower and burner, and a (usually) extensive network of metal ductwork, working together to provide you and your family with warmth and comfort. The mysterious noises it might make could seem pretty baffling at first, but with a little investigative work, you can usually pinpoint (or at least narrow) the area of origin.

Rushing Air, a.k.a. “Huffing and Puffing”

You’re no doubt accustomed to hearing the gentle sound of air blowing through your vents as your furnace runs in the Winter. That’s to be expected, right? But if you’re hearing a sound like rushing wind that’s loud enough to wake you (or keep you awake!), then your furnace might have developed some air leaks near the plenum (the chamber connecting your main duct to the furnace).

Take a look: Double-check the seams to make sure they’re sealed tightly. If any existing duct tape has dried out and blown loose, it might be allowing air to escape. Replace the tape and have a word with your local HVAC pro at your next scheduled maintenance call to make sure there’s not a larger issue at work.

“The Rumble”

If you hear an ominous rumble or vibration coming from your furnace room, it’s possible your furnace is not secured properly to the wall or floor.

Take a look: Do a quick check to make sure all the bolts, screws, and other hardware are firmly tightened and positioned correctly. If necessary, give the wall itself a once-over to make sure it’s in good condition. If any parts need repaired or replaced, do so as quickly as possible, or speak to your technician.

“The Factory Floor”

As we’ve discussed, your furnace is going to make a certain amount of noise just doing its job. But If it sounds like you’re standing on the floor of a machine shop or right next to the 3:10 to Albuquerque when you’re near your furnace, it’s time to investigate.

Take a look: Excessive noise might mean your “extra noisy furnace” is just working harder than it has to due to restricted airflow, debris, or dirt. Start by making sure your furnace filter is clean and in good working order. Then check for anything else that might be restricting airflow, such as blocked registers and vents, obstructions in the ducts themselves, or even closed directional flaps on the vent covers. The cleaner and clearer the airflow, the more easily your furnace can “breathe”—and the less noise it’ll make.

“The Squeaky Wheel”

They say the squeaky wheel gets the oil, but in this case, you might need to make a service call instead.

Take a look: This particular noisy furnace symptom usually indicates a belt or bearings need tending to, so if you’re not mechanically inclined, give your local HVAC expert a call. If you’re a little more hands-on, you can consult your furnace’s user manual for information on how to access and oil (if necessary) your drive belt. If the issue isn’t the belt, it might be your bearings in the motor driving the belt. In either case, it’s usually best to put in a service call, just to be sure.

Whether your furnace is humming along like a champ (or grumbling like a Grinch!), taking a few moments to identify any unusual noises can help keep your system running smoothly. You’ll head off potential future headaches, and make sure your family and home are nice and warm throughout the holidays and in the year ahead.

Silent Night, Noisy Furnace? Diagnosing Furnace Noise
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