A furnace is almost always a background player for your home, keeping you warm in the cold winter months. It often doesn’t get noticed until a malfunction appears. 

One root cause could be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s worthwhile to familiarize yourself with the evidence of a cracked heat exchanger and what you should do if you are worried that is 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 circulates through the air ducts. It typically does this with coils or tubes that heat up the air while serving as a barrier to keep the gasses formed 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 pose a risk. A damaged heat exchanger can allow dangerous gasses – such as carbon monoxide, which can be lethal – to circulate through your home. 

For this reason, do NOT use your heater if you think there's a crack in the heat exchanger, as doing so could make the whole household sick. Contact an HVAC professional right away if you believe your furnace has a cracked heat exchanger that needs repair. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: A cracked heat exchanger could cause your furnace to shut off. 
  • Unusual Smells: If the air leaving your furnace has a strong chemical scent, it could be an indicator that gasses are leaking through cracks in your heat exchanger. These byproducts, which can smell like formaldehyde, are a common warning sign. 
  • Carbon monoxide alarm initiates or you recognize symptoms of poisoning: If a cracked heat exchanger is relieving carbon monoxide in your home, your carbon monoxide alarm may go off or household members could experience signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If an alarm goes off or you feel unwell, get out of the home right away and then call for help. 
  • Soot: If you see black sooty buildup around the exterior of your furnace, it’s more evidence something might be seriously wrong.

What to Do if a Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, hire a professional experienced in furnace installation Marshfield right away so they can inspect your system and, if needed, perform a furnace heat exchanger replacement. Costs will vary depending on the situation, but estimates run in the neighborhood of $1,000 to $3,000. 

Fortunately, the good news is that heat exchangers are regularly protected by the warranty. You’ll want to confirm the warranty paperwork on your furnace, since while the warranty may not cover the entire cost of repairs, it could significantly shrink your bill.  

How to Avoid 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. Hiring a trained professional to check your furnace for worn-out parts, clogged filters and other potential problems can help you avoid getting a big bill later on.  

It’s also a good idea 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 a part of 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 works, the more deterioration pieces like the heat exchanger will sustain.