A furnace is almost always a background player at home, helping keep you warm in the cold winter months. It regularly doesn’t get noticed until something goes wrong. 

One source might be that your furnace has a cracked heat exchanger. It can be a safety risk, so it’s critical to know the evidence of a cracked heat exchanger and what you should do if you suspect that is the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber inside your furnace to the air that flows inside the ventilation. It typically 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? 

Thanks to its important role, it’s no surprise that a cracked heat exchanger can be very dangerous. Cracks in the heat exchanger can permit dangerous gasses – such as carbon monoxide, which can be lethal – to circulate through your home. 

For that reason, never run your furnace if you believe there's a crack in the heat exchanger, as doing so could make your entire family sick. Contact an HVAC professional immediately if you are worried your heating has a cracked heat exchanger that should be repaired. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace switches off: Cracks in the heat exchanger can cause your furnace to turn off. 
  • Odd Smells: If the air escaping your furnace has a powerful chemical odor, it might be evidence gas is slipping through cracks in your heat exchanger. These byproducts, which may smell like formaldehyde, are a common warning sign. 
  • Carbon monoxide alarm goes off or you feel symptoms of poisoning: If a cracked heat exchanger is emitting carbon monoxide into your home, your carbon monoxide alarm may go off or family members may struggle with signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If the alarm goes off or you feel unwell, exit the home right away and then call for help. 
  • Soot: If you find black sooty accumulating near 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 suspect your furnace has a cracked heat exchanger, contact a professional with extensive experience in furnace installation Wausau right away so they can inspect your system and, if necessary, handle a furnace heat exchanger replacement. Costs often vary depending on the situation, but estimates can roughly suggest $1,000 to $3,000. 

However, the good news is that heat exchangers are regularly included in the warranty. You should check the warranty paperwork on your furnace, since while the warranty may not cover the entire cost of repairs, it still may significantly lower your bill.  

How to Avoid a Cracked Heat Exchanger in Your Home  

One of the most convenient ways to prevent a problem in your furnace overall is through consistent furnace maintenance. Furnaces provide the best possible return on investment when they run efficiently. Contacting a trained professional to inspect your furnace for worn-out parts, dirty filters and other common problems can keep you from getting a big bill later on.  

It’s also helpful to review 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 a part of the heat exchanger itself, the strain of dragging air through a clogged filter makes the entire furnace work harder to accomplish its job. And the harder your furnace needs to run, the more strain pieces like the heat exchanger will endure.