5 Reasons Why Furnaces Make Loud Noises

“Aren’t modern HVAC systems supposed to be quieter than ever?” you may find yourself wondering. “So why does my furnace sound so loud?”

Yes, you’re right. Today’s technology has given us efficient furnaces which operate quietly … most of the time. If your furnace is rattling, screeching, or banging, it is telling you something’s wrong.

The experts at Ottawa Home Services, Ottawa’s furnace installation and furnace repair experts, have the answers. Read on to find out the source of the noises coming from your furnace, and how serious the problems may be.

Noises That Require Action

Never simply ignore any of the noises listed below. They may be signalling a problem that is dangerous to your furnace (and perhaps to your home). Instead, contact a reliable heating and cooling company and ask them for answers about your furnace issue.

High pitched screeching or whistling
Rattling
Banging or booming
Scraping sound

Causes of Loud Noises:

1. Dirty Furnace Filter

The simplest explanation for screeching or whistling is that your furnace air filter could be clogged with dust, hair, and dirt. That eerie screech you hear might just be air desperately trying to get through.

Fortunately, you can take care of this noise issue yourself, quickly and inexpensively. If you use disposable filters, replace the existing filter with a fresh one (or clean the filter if it is a permanent version).

If you don’t have a spare disposable, it’s actually better to remove the old one and operate your furnace without a filter for a day or two until you can get yours from Ottawa Home Services. Otherwise, the clogged filter will continue to restrict airflow to the point where your furnace’s fan motor or heat exchanger might become seriously damaged.

TIP: Check your air filter every 30 days and change or clean it at least once every three months. Always keep a backup supply of disposable filters on hand.

2. Blower Motor

Another potential reason for screeching sounds is your blower motor, the power source for the blower that forces warmed air through your ductwork to heat your home. The blower motor requires sufficient lubrication to do its job properly (and quietly). If it runs too low on oil, your blower motor may damage the furnace as a whole.

TIP: The furnace blower motor should be lubricated once a year by applying 2-3 drops of motor oil to the oil ports.

3. Blower Wheel

The blower wheel (the component powered by the blower motor to move heated air) will sometimes start to make a harsh scraping, metal-against-metal sound as it rotates. This sound indicates that the blower wheel is out of alignment and needs expert adjustment.

TIP: For peak performance, the blower wheel must be kept clean. Annual furnace maintenance by an experienced HVAC company will ensure the blower wheel is functioning correctly.

4. Cracked Heat Exchanger

Rattling noises could indicate your heat exchanger is taking its last breath. When you don’t clean your furnace and change the filter regularly, airflow becomes restricted. Eventually, your furnace will reach the point where heat buildup could crack the heat exchanger.

A cracked heat exchanger is extremely hazardous, as it can cause leakage of carbon monoxide – a colourless, odourless, but highly lethal gas. If you suspect this is your problem, turn off the furnace and get a qualified HVAC technician to take care of this repair as soon as possible.

TIP: Install a carbon monoxide alarm to monitor levels of this deadly gas. Also, schedule regular professional furnace maintenance to ensure your heating system is safe and in working order.

5. Dirty Burners

Do you hear a boom or bang (almost like an explosion) a few seconds after you switch on your furnace? This is a sign that you might have dirty burners, which are causing a delayed ignition – and that explosion is a definite danger signal.

Fortunately, a professional furnace cleaning will take care of the problem. TIP: Schedule a regular yearly furnace tuneup to stop problems like this one before they even start.

6. Duct Issues

Your HVAC ducts are made of thin sheet metal, so they are excellent at carrying sounds. When your ducts start rattling and banging, it could be due to a change in pressure between the supply and return ducts.

Alternatively, they may need reinforcement; either the ductwork has come loose from the walls in one or two places, or there are weak spots in the ducts themselves. While none of these issues is a dire furnace repair emergency, it is important to have your ductwork inspected and repaired by a professional.

TIP: Listen carefully and try to pinpoint exactly where the sound is coming from, before you call a tech. This information will lead to a faster, more accurate diagnosis.