A furnace is often a background player for your home, helping keep you warm across the cold winter months. It regularly won't be noticed until something breaks down. 

One root cause may be that your furnace has a cracked heat exchanger. It can be a safety risk, so it’s critical to familiarize yourself with the evidence of a cracked heat exchanger and what to do if you suspect that might be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber in your furnace to the air that moves through the ventilation. It generally accomplishes this through coils or tubes that heat the air while functioning as a barrier to keep byproducts created in the combustion chamber, called flue gasses, from getting out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Because of its important role, it isn't surprising that a damaged heat exchanger can be very dangerous. A crack in the heat exchanger can allow dangerous gasses – including carbon monoxide, which can be lethal – to flow through your home. 

For that reason, never turn on your heating if you believe you're dealing with a cracked heat exchanger, as doing so could make the whole household ill. Contact an HVAC professional immediately if you are worried your heating has a cracked heat exchanger that needs repair. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: A crack in your heat exchanger can cause your furnace to shut off. 
  • Unusual Smells: If the air leaving your furnace has a powerful chemical odor, it may be an indicator that gasses are slipping through cracks in your heat exchanger. These gasses, which can smell like formaldehyde, are a significant warning sign. 
  • Carbon monoxide alarm initiates or you notice poisoning symptoms: If a cracked heat exchanger is relieving carbon monoxide into your home, your carbon monoxide alarm may go off or family members may struggle with signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If an alarm goes off or you feel unwell, leave the home immediately and then call for help. 
  • Soot: If you find black sooty buildup on the exterior of your furnace, it’s another sign something might be seriously wrong.

What to Do if Your Furnace Heat Exchanger is Cracked 

If you worry your furnace has a cracked heat exchanger, hire a professional experienced in furnace installation Wilmington right away so they can inspect your system and, if necessary, perform a furnace heat exchanger replacement. Costs will vary depending on the situation, but estimates can roughly suggest $1,000 to $3,000. 

However, the good news is that heat exchangers are generally included in the warranty. It's a good idea to confirm the warranty paperwork on your furnace, because while the warranty won't always cover the entire cost of repairs, it can significantly lower your bill.  

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the most convenient ways to prevent a problem in your furnace overall is via regular furnace maintenance. Furnaces work the best when they run efficiently. Calling a certified professional to examine your furnace for broken-down parts, dirty filters and other potential problems can keep you from getting a big bill later on.  

It’s also helpful to inspect your furnace filters every few months – it’s ideal some filters be replaced 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 dragging air through a clogged filter makes your entire furnace work more vigorously to complete its job. And the harder your furnace works, the more deterioration parts like the heat exchanger will experience.