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Why Is My Furnace So Loud?

By Carrie Dixon, Blog Editor

Loud furnace making noisesYour furnace is responsible for keeping the house warm during the winter months. However, sometimes it’s not as simple as just clicking on, warming the air and then blowing that air through the ducting to warm up the home. Sometimes, there’s a great deal of noise involved with furnace operation. Wondering why your furnace is so loud? Actually, there are quite a few potential reasons depending on the type of noise you’re hearing.

There’s a rattling noise

If you’re experiencing a rattling or vibrating sound, it could be one of several potential issues. First, it could be that you need more support for your ducting (screws). You’ll need to check the ductwork to see if any sections are loose, and then add screws to support those areas. There’s also the possibility that the rattling is from the furnace itself (it’s uneven, and wobbling during operation). Placing cork pads under the furnace corners can help here.

There’s a squealing noise

If the furnace kicks on and you hear a squealing sound, it may be a problem with the blower motor. In many instances, it involves the bearings on the blower motor fan, but that’s not always the case. In belt-driven systems, it could be a loose belt that is beginning to slip. If you have a heat pump, it could be related to a noisy or failing check-valve, or even to a low refrigerant level.

There’s a strange rumbling sound

If you hear a rumbling sound and your furnace is gas or oil based, turn the system off immediately. Rumbling from one of these units usually indicates a burner issue that must be taken care of by a professional before the system is used again. To reiterate – turn off the system if you hear a rumbling noise, and it uses either gas or oil as fuel.

There’s a humming sound

With most furnaces, a humming sound during operation is pretty normal. This is particularly true for electric furnaces. The sound is just the transformer working. You may notice an increase in the humming after having the transformer replaced in an older furnace. That’s because some transformers hum more loudly than others. Usually, it’s not a cause for concern. However, it may be a sign that the transformer is failing if you’ve noticed the humming sound getting louder and haven’t had any work done on the system.

The unit turns on and off repeatedly

There are a couple of reasons that your furnace might cycle constantly. One of the most common, particularly in areas where very cold weather is common, is that it’s just cold out and your home is losing heat rapidly. The unit cycles to maintain the temperature you’ve selected. You can choose a lower temperature and the unit may be able to maintain it without frequent cycling. Another possibility is that your home has lost insulation or developed leaks over the years, and the unit is cycling constantly because you’re losing heated air to the environment. Of course, there’s also the possibility that the thermostat is beginning to fail and is in need of replacement.

The bottom line

Whatever the cause of your furnace noise, it’s important to have it checked out by a reputable HVAC professional. In many cases, it might be nothing at all. However, it could just as easily be a serious problem that requires professional repair. Finally, remember that regular maintenance can save you a great deal of hassle down the road by catching potential issues before they become real problems.