Why Is Your Furnace's Draft Inducer so Noisy?

Draft inducer motors (also known as exhaust blowers) are a feature found on nearly every modern furnace. These motors improve efficiency by forcing combustion gases through your exhaust flue rather than waiting for them to rise out of the furnace naturally. High-efficiency units rely on draft inducers since they extract so much heat from the exhaust stream. 

Your inducer motor is typically the first thing you'll hear as your furnace comes on since the burners won't ignite without an adequate exhaust draft. A failing draft inducer can produce numerous symptoms and may also stop your furnace from operating at all. Rattling or grinding is a common warning sign, but there are many potential reasons why the draft inducer might make these sounds.

Identifying Draft Inducer Noises

Modern furnaces follow a relatively standardized ignition sequence. One of the first things your furnace will do is turn on the draft inducer. This step will occur before the furnace burners or your house blower comes on, so the draft inducer will engage before you feel the heat from your vents. If you stand near your furnace, you'll usually hear the sound of a fan engaging as your thermostat calls for heat.

If you can hear a rattling, clicking, or grinding noise, it's usually relatively easy to isolate it to the draft inducer. The best option is usually to stand near your furnace as it comes on. You should hear the draft inducer turn on first, followed by the sound of the burners igniting, and finally, your house blower will turn on to distribute heat.

You can usually tell if the inducer motor is the cause of your problem by paying close attention to this sequence of operations. Noises that occur before the burners ignite are nearly always produced by the inducer motor. On the other hand, any noises that happen later in the ignition sequence may be coming from another component.

Common Causes of Draft Inducer Noise

A light rattling or vibrational noise from your draft inducer may not indicate a severe problem. In some cases, the housing may work itself loose, causing the screws that hold it in place to rattle. Foreign objects can also enter the housing, bouncing around on the blades and causing loud noises. If you can remove your furnace cover, you may be able to identify these noises relatively easily.

On the other hand, a noisy inducer may indicate worn-out bearings. Like most electrical motors, your inducer uses lubricated bearings to operate smoothly. These bearings can fail over time, losing their lubrication and producing excess friction and heating. In these cases, you'll usually hear a loud grinding, and that's a good indication that your inducer motor may fail shortly.

In general, it's not a good idea to ignore inducer noise. If the problem is a foreign object, allowing it to remain in the housing can damage the blower blades and cause more problems in the future. Likewise, a failing motor will eventually stop your furnace from working. Addressing the issue now can ensure your furnace continues to provide reliable heat. Talk to heating services for more information.