Skip to content
A furnace is almost always a background player in your home, ensuring you're warm across the cold winter months. It often doesn’t get noticed until a malfunction appears.
One root cause may be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s important to familiarize yourself with the evidence of a cracked heat exchanger and what to do if you believe that may be the problem.
What Is a Heat Exchanger in a Furnace?
A heat exchanger helps transition heat from the combustion chamber in your furnace to the air that moves throughout the ventilation. It generally accomplishes this with coils or tubes that heat the air while serving as a barrier to keep the gasses produced in the combustion chamber, called flue gasses, from getting out into your home.
Is a Cracked Heat Exchanger Dangerous?
Thanks to its central role, it isn't surprising that a cracked heat exchanger can pose a risk. Cracks in the heat exchanger can allow dangerous gasses – like carbon monoxide, which can be lethal – to circulate through your home.
For this reason, do NOT run your furnace if you think it has a cracked heat exchanger, as doing so could make your entire household sick. Reach out to an HVAC professional immediately if you think your furnace has a cracked heat exchanger that should be repaired.
Four Warning Signs of a Cracked Heat Exchanger:
- Furnace turns off: A crack in your heat exchanger may cause your furnace to turn off.
- Unusual Smells: If the air leaving your furnace has a strong chemical odor, it might be a sign gasses are slipping through cracks in your heat exchanger. These gasses, which will often smell like formaldehyde, are a significant warning sign.
- Carbon monoxide alarm goes off or you feel health problems: If a cracked heat exchanger is relieving carbon monoxide in your home, your carbon monoxide alarm may go off or household members may experience signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If an alarm goes off or you feel sick, get out of the home as soon as you can and then call for help.
- Soot: If you notice black sooty collecting near the exterior of your furnace, it’s more evidence something may be seriously wrong.
What You Should Do if Your Furnace Heat Exchanger is Cracked
If you worry your furnace has a cracked heat exchanger, hire a pro well versed in furnace installation as soon as possible so they can examine your system and, if required, start a furnace heat exchanger replacement. Costs should differ depending on the situation, but estimates run in the neighborhood of $1,000 to $3,000.
Estimates aside, the good news is that heat exchangers are generally protected by the warranty. You should review the warranty paperwork on your furnace, as while the warranty might not cover the entire cost of repairs, it still may significantly shrink your bill.
How to Prevent a Cracked Heat Exchanger in Your Home
One of the best ways to avoid problems in your furnace overall is via consistent furnace maintenance. Furnaces provide the best possible return on investment when they run efficiently. Contacting a certified professional to inspect your furnace for worn-out parts, clogged filters and other common problems can help you avoid getting a big bill later on.
It’s also helpful to take a look at your furnace filters every few months – it’s ideal some filters be swapped out every 90 days or sooner if they are dirty or grimy. While the filters aren't connected to the heat exchanger itself, the strain of drawing air through a clogged filter makes the entire furnace work harder to accomplish its job. And the harder your furnace has to work, the more deterioration pieces like the heat exchanger will experience.