If there’s one thing that can’t be said about furnaces, it’s that they’re quiet. You may be used to the sound of the furnace roaring to life when you turn it on, or you may hear a humming noise as you pass the closet in which the furnace is stored. At some point, it all becomes white noise. However, there are certain furnace noises that go beyond the norm and probably shouldn’t be ignored. If you hear these noises, in fact, it might be a good idea to contact your HVAC technician. But how can you tell when a noise coming from your furnace is really a problem and what those noises mean? Here’s our helpful guide:
Typical Furnace Sounds
Again, not all furnace noises are wrong, per se. You may hear a humming noise when the burner starts or soft rattling as the system starts to cool down. You may even hear occasional crackling during the cool down process. All of this is standard operation. You can expect to hear some expanding and contracting of the ducts, although the noise will be quite different if there’s a struggle with the air ducts (we’ll get to that later).
Scraping and Scratching
Does it ever sound like an animal is scratching against your furnace or like something is scraping against the surface? While that’s probably not the case — and lucky that it’s not in the animal’s case — a scraping noise is definitely something to take note of. The sound of scraping metal could mean that your blower wheel is broken or that something inside the furnace has come loose. If this goes ignored, the furnace might break down, so it’s a good idea to address this as soon as you can.
A booming noise coming from your furnace is likely to cause concern, but without knowing what it means, you might simply wonder if that’s standard operation for a furnace, especially an old furnace. It is not; however, there could be a few causes. It may be that the burner is covered in dust, which makes it more difficult to operate. There could be a gas buildup or the ignition when the burner finally lights could cause damage to the interior of the furnace. It could also mean that there’s a problem with the air ducts in your home: maybe they’re too small, a screw is loose, or the air filters are clogged.
Does your furnace shake the house as it finishes running? It shouldn’t. Those deep rumbling noises spell problems for your furnace, as well. Typically, this happens when excess oil continues to burn even after the burner is shut off. There could also be an issue with the pilot light or flame sensor. If ignored, this problem could lead to a release of carbon monoxide into your home, a gas that can and has been deadly for homeowners.