Why Is My Furnace Louder Than Normal?

Your heating system will always be a bit louder than your air conditioning. This is because your furnace is inside, whereas the main AC unit is outside your home. Nonetheless, if your furnace ever starts making more noise than normal or you hear any unusual sounds when it is running, it usually indicates that there is some issue with the system. Depending on the specific cause, you may need to have your heating system inspected and serviced by a professional technician. Let’s review the various issues that can cause a furnace to run loudly or make strange noises and what can be done to fix the problem.

Clogged Air Filter or Return Vents

If your furnace is suddenly much louder the entire time it is running, it typically indicates that there is some issue causing your heating system to work much harder. In most cases, the loud noises you’re hearing are because the blower is working overtime due to something restricting the airflow in the system.

The most common thing that leads to restricted airflow is a dirty air filter, and this is always the first thing to check whenever your furnace is running more loudly. The blower draws air in through your home’s return vents. The air passes through the return ducts and is then drawn through the air filter before it enters the furnace.

If you don’t remember to change your air filter every month or two, it will eventually become so coated in dust and debris that very little air can flow through it. Restricted airflow can also result if the supply vents are clogged with hair and dust or obstructed by furniture. Either issue will put added strain on the blower fan and can cause it to run louder since it has to work much harder to draw air in.

Dirty Gas Burners

There are often times when a furnace will start making a loud booming sound whenever it first lights, and this problem generally always means that the unit’s gas burners are dirty and need to be cleaned. If you don’t have a technician maintain your furnace regularly, the burners will start to become clogged with soot and grime.

If the burners are dirty, it will often lead to a slight delay before they ignite. Even a slight delay in combustion means that gas will begin filling the burner chamber before the unit ignites, and this will produce a small fireball or miniature explosion once the burners finally light. You can think about this as similar to the fireball that a gas barbecue grill can produce if you don’t light it immediately after turning the gas on.

This is one issue that you shouldn’t wait to get taken care of as the force and heat from the fireball has the potential to cause major damage to your furnace. Although there is very little risk of the furnace exploding, this issue could cause the heat exchanger to crack and carbon monoxide to begin leaking out into your home.

Worn-Out Bearings or Belt in the Blower Motor

A loud screeching or squealing noise whenever your heating system is running is a sign that there is some issue with the blower motor. Newer blowers have direct-drive motors that use sealed bearings to spin, and these bearings can begin to wear out due to age and start making high-pitched noises. If your blower motor is older, it most likely uses a belt-drive motor similar to the belt found in your car. Just like in your car, this belt will start squealing if it begins to wear out or becomes misaligned.

Both types of motors can typically be repaired quite easily by replacing the bearings or the fan belt. However, it is important that you get this done as soon as possible. Otherwise, you run the risk of the motor overheating and burning out.

Misaligned or Loose Blower

A grinding noise or anything that sounds like metal scraping on metal is also generally caused by the blower. Over time, the blower can get misaligned or start to come loose from its housing, and this can result in it scraping up against the housing as it spins. While not as serious as some other issues, this is still something you should have checked out as soon as possible since it could ruin the blower and force you to have it replaced.

Loose, Damaged or Leaking Air Ducts

Loud whistling sounds when your heating system is running usually indicate that your ductwork is damaged, not fully sealed, or otherwise leaking air. Some air will always escape if there are any gaps, cracks, or holes in the duct system, and this air will often escape with such force that it produces an audible whistling sound. Ductwork can also produce loud rattling noises if it has started to sag or come loose or if two sections of ductwork no longer fit tightly together.

Ductwork issues aren’t nearly as serious of a problem. Nonetheless, they will lead to increased energy costs and decrease the effectiveness of your heating and air conditioning system, so they are still not something you’ll want to ignore for too long.

Cracked Heat Exchanger

Of all of the different furnace issues, a cracked heat exchanger is the one you definitely want to hope to avoid as it greatly increases the risk of potentially fatal carbon monoxide poisoning. Not only will a cracked heat allow carbon monoxide to escape, but it will also drastically limit how much heat your furnace produces.

If your heat exchanger is cracked, you will usually need to have your furnace replaced. A technician can replace the heat exchanger, but typically the only time this ever makes much sense is when the furnace is relatively new and the heat exchanger is still under warranty. If it’s not under warranty, then replacing the heat exchanger will usually cost about the same as having a whole new furnace installed.

A small crack in the heat exchanger is often nearly impossible to detect, and the first sign is usually when the home’s carbon monoxide detectors start going off. If the heat exchanger has a major crack or the connections between it and the combustion chamber are loose, the furnace will sometimes produce a loud rattling sound whenever it runs. You may also notice a formaldehyde-like smell coming from your furnace or vents when the heat exchanger is cracked. If you do ever notice any of these issues, you should immediately turn your heating system completely off and wait to use it again until you can have it inspected.

At Blue Best Plumbing, Heating, Air, Generators, our technicians can help determine why your furnace is making so much noise and how best to fix it. We repair all brands and types of furnaces as well as air conditioners, heat pumps, ductless mini-splits, and fireplaces, and we also specialize in heating and cooling installation and maintenance. We are proud to be a BBB-accredited business focused on excellent service. Give us a call today to schedule a furnace inspection or if you need any other heating or cooling service in Bountiful or the Greater Salt Lake City area.

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