A furnace is almost always a background player in your home, keeping you warm across the cold winter months. It frequently isn't noticed until something goes wrong. 

One root cause may be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s critical to know the signs of a cracked heat exchanger and what you can do if you believe that might 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 flows through the air ducts. It usually does this using coils or tubes that warm the air while acting as a barrier to keep gas produced in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Thanks to its key role, it shouldn't come as a surprise that a broken heat exchanger can be hazardous. A crack in the heat exchanger can enable dangerous gasses – like carbon monoxide, which can be lethal – to be distributed across your home. 

For obvious reasons, don't ever run your furnace if you think there's a crack in the heat exchanger, as this could make the entire family ill. Contact an HVAC professional immediately if you are worried your furnace has a cracked heat exchanger that should be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace turns off: A cracked heat exchanger may cause your furnace to turn off. 
  • Strange Smells: If the air escaping your furnace has a powerful chemical odor, it could 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 is triggered or you feel health problems: If a cracked heat exchanger is emitting carbon monoxide in your home, your carbon monoxide alarm should go off or household members might start experiencing signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If your alarm goes off or you feel sick, leave the home right away and then call for help. 
  • Soot: If you find black sooty buildup on the exterior of your furnace, it’s more evidence something could be seriously wrong.

What You Should Do if the Furnace Heat Exchanger is Cracked 

If you suspect your furnace has a cracked heat exchanger, hire a professional experienced in furnace installation Des Moines right away so they can take a look at your system and, if required, handle a furnace heat exchanger replacement. Costs will vary depending on the situation, but estimates often hover around $1,000 to $3,000. 

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

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the easiest ways to minimize the risk of problems in your furnace overall is with routine furnace maintenance. Furnaces work the best when they operate efficiently. Hiring a certified professional to check your furnace for old parts, clogs in the air filters and other likely 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 encouraged 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 the entire furnace work longer to complete its job. And the harder your furnace has to work, the more wear and tear parts like the heat exchanger will endure.