Signs Your Furnace’s Heat Exchanger Is Failing

The heat exchanger is a major part of a gas furnace. It extracts heat from the combustion chamber (which is sealed to contain toxic flue gases) to warm the air pushed through it. Heated air is then delivered to your home via the blower. 

A failing or cracked heat exchanger can cause toxic gases, including carbon monoxide, sulfur dioxide, and nitrogen dioxide, to be released, putting your entire family in danger. Therefore, it’s critical you know the signs of trouble to look for.

How Does My Heat Exchanger Work?

It is an assembly consisting of coils and tubes. Enclosed in a metal chamber, the exchanger allows hot combustion gases in through tubes, which heat its metal walls. Cold air from return ducts is blown over the coils heated by the furnace, and in turn, becomes warmer. Conditioned air is then blown into the supply ducts to each room, while combustion gases are vented outside.

When to Suspect Heat Exchanger Failure

When the component is damaged, it often doesn’t look so from the outside. But a few symptoms point to a failing heat exchanger. Call a furnace repair technician if you notice any of the following:

The Burner Flame Is Yellow or Orange

The flame should always be blue. This means everything is working fine. If you see a flickering yellow flame, it means there’s a problem with the combustion process and oxygen may be reaching the chamber. A dirty burner can be the reason, but a cracked heat exchanger is also a possibility.

The Furnace Is Producing Soot

A crack can cause soot to build up on the exchanger. The soot originates from the combustion chamber; it may collect at the site of the crack or inside the furnace because the gas isn’t burning completely. As a result, carbon buildup forms. Soot may also collect in or around the furnace’s burners.

Strong Odors Occur Around the Furnace

An unpleasant smell, possibly similar to formaldehyde, is a sure sign of a problem. Your heating system should not emit strong odors. You might notice a slight burning smell when starting up the unit for the season. This should not last long, but if it does and/or the odor is strong and unpleasant, call for help.

You Hear the Carbon Monoxide Alarm

While other combustion gases have a noticeable odor, carbon monoxide (CO) doesn’t. It also has no color or taste, yet is deadly in high concentrations, and flammable. If your CO detector goes off, leave your home and call for help. Also, schedule annual furnace inspections to find and fix issues early. 

Your Furnace Makes Unusual Noises

A cracked heat exchanger can cause a rattling, popping, or banging noise. Throughout the heating process, cracked metal will expand and contract. This creates audible cues that something is wrong. The problem will only get worse if ignored.

Visible Signs of Damage

Corrosion, stress cracks, and other signs of wear on the furnace should be checked by a professional. Water on the floor, if there isn’t a condensation issue, can mean the heat exchanger is bad. Other potential causes include a leaking humidifier or clogged HVAC drain.

Why Did My Heat Exchanger Fail?

The component can fail due to overheating, dust accumulation (which can overheat the system), and frequent alternation between heating and cooling. Constant expansion and contraction will cause it to wear out. Rust, corrosion, and the age of your furnace can also play a role in the exchanger cracking or otherwise failing. Furnaces over 15 years of age are at a higher risk of developing a cracked heat exchanger, which reduces efficiency and creates many hazards.

Contact an HVAC Professional If Your Heat Exchanger Is Failing

If you notice any of the signs above or otherwise suspect a problem with your furnace, don’t try to fix it yourself. Turn off your heating system and call an HVAC contractor to inspect it. A damaged exchanger must be replaced. But if your furnace is over 15 years old, the technician will most likely suggest replacing the entire unit.
Homeowners in Olympia, WA, can rely on Black Hills for furnace maintenance and repair. We also replace older systems with more efficient models. Available 24/7, we can respond to any heating emergency. Our technicians are licensed and bonded as well as trained to quickly address heat exchanger and other problems. To request service, contact us online or call 888-743-1041 today.