A furnace is usually a background player for your home, helping keep you warm in the cold winter months. It often doesn’t get noticed until something breaks down. 

One root cause might be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s critical to familiarize yourself with the signs 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 transfers heat from the combustion chamber of your furnace to the air that moves inside the air ducts. It usually accomplishes this through coils or tubes that warm 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? 

Given its important role, it’s no surprise that a cracked heat exchanger can be hazardous. A damaged heat exchanger can permit dangerous gasses – like carbon monoxide, which can be lethal – to be distributed throughout your home. 

For obvious reasons, never use your heating if you suspect it has a cracked heat exchanger, as this could make the entire household sick. Reach out to 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 shuts off: A crack in your heat exchanger may cause your furnace to switch off. 
  • Unusual Smells: If the air coming out of your furnace has a powerful chemical scent, it might be an indicator that gas is seeping through cracks in your heat exchanger. These byproducts, which can smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm goes off or you recognize symptoms of poisoning: If a cracked heat exchanger is emitting carbon monoxide inside your home, your carbon monoxide alarm could go off or household members might experience signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If an alarm goes off or you feel unusually tired, leave the home as soon as you can and then call for help. 
  • Soot: If you find black sooty accumulating on the exterior of your furnace, it’s more evidence something may be seriously wrong.

What You Can Do if a Furnace Heat Exchanger is Cracked 

If you suspect your furnace has a cracked heat exchanger, call a professional with extensive experience in furnace installation Pella right away so they can inspect your system and, if needed, handle a furnace heat exchanger replacement. Costs will differ depending on the situation, but estimates run in the neighborhood of $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, since while the warranty won't always cover the entire cost of repairs, it could 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 routine furnace maintenance. Furnaces work the best when they work efficiently. Hiring a skilled professional to check your furnace for worn-out parts, clogged filters and other common 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 recommended some filters be changed every 90 days or sooner if they are dirty or grimy. While the filters are not part of the heat exchanger itself, the strain of dragging air through a clogged filter makes your entire furnace work harder to accomplish its job. And the harder your furnace needs to run, the more deterioration pieces like the heat exchanger will sustain.