A furnace is almost always a background player at home, keeping you warm during the cold winter months. It frequently doesn’t get noticed until a malfunction appears. 

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

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps move heat from the combustion chamber in your furnace to the air that flows inside the system. It typically handles this through coils or tubes that warm the air while functioning as a barrier to keep the gasses produced in the combustion chamber, called flue gasses, from escaping out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Given its central role, it isn't surprising that a cracked heat exchanger can be very dangerous. Cracks in the heat exchanger can enable dangerous gasses – such as carbon monoxide, which can be lethal – to circulate throughout your home. 

For this reason, don't ever turn on your furnace if you believe there's a crack in the heat exchanger, as letting it run could make the whole household ill. Call an HVAC professional right away if you are worried your heater has a cracked heat exchanger that needs repair. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: Cracks in the heat exchanger can cause your furnace to switch off. 
  • Unusual Smells: If the air escaping your furnace has a powerful chemical scent, it could be a sign gasses are leaking through cracks in your heat exchanger. These gasses, which will often smell like formaldehyde, are a common warning sign. 
  • Carbon monoxide alarm goes off or you notice poisoning symptoms: If a cracked heat exchanger is emitting carbon monoxide into your home, your carbon monoxide alarm may go off or family members could struggle with signs of carbon monoxide poisoning. Complications include headaches, dizziness, weakness, nausea, vomiting or feeling drowsy. If an alarm goes off or you feel unwell, exit the home as soon as you can and then call for help. 
  • Soot: If you see black sooty collecting near the exterior of your furnace, it’s another sign something could be seriously wrong.

What to Do if the Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, contact a pro well versed in furnace installation Marshalltown right away so they can inspect your system and, if necessary, 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. 

Fortunately, the good news is that heat exchangers are often covered by the warranty. You should check the warranty paperwork on your furnace, as while the warranty might not 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 avoid problems in your furnace overall is with regular furnace maintenance. Furnaces provide the best possible return on investment when they work efficiently. Calling a skilled professional to inspect 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 helpful to take a look at 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 pulling air through a clogged filter makes the entire furnace work more vigorously to accomplish its job. And the harder your furnace needs to run, the more strain pieces like the heat exchanger will experience.