A furnace is often a background player in your home, ensuring you're warm during the cold winter months. It often isn't noticed until a malfunction appears. 

One source could be that your furnace has a cracked heat exchanger. It can be a safety risk, so it’s important to familiarize yourself with the signs of a cracked heat exchanger and what to do if you are worried that may be 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 flows inside the system. It usually accomplishes this via coils or tubes that heat the air while functioning as a barrier to keep gas created in the combustion chamber, called flue gasses, from getting out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

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

For obvious reasons, don't ever turn on your furnace if you suspect it has a cracked heat exchanger, as doing so could make your entire household ill. Reach out to an HVAC professional immediately if you believe your heater has a cracked heat exchanger that should be repaired. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace switches off: A cracked heat exchanger can cause your furnace to switch off. 
  • Odd Smells: If the air leaving your furnace has a strong chemical odor, it may be an indicator that gas is seeping through cracks in your heat exchanger. These byproducts, which will often smell like formaldehyde, are a significant warning sign. 
  • Carbon monoxide alarm initiates or you notice poisoning symptoms: If a cracked heat exchanger is relieving carbon monoxide into your home, your carbon monoxide alarm should go off or household members could start experiencing signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If your alarm goes off or you feel unwell, exit the home as soon as you can and then call for help. 
  • Soot: If you spot black sooty buildup near the exterior of your furnace, it’s an indication something could be seriously wrong.

What You Should Do if a Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, contact a professional experienced in furnace installation Wausau right away so they can take a look at your system and, if needed, perform a furnace heat exchanger replacement. Costs will differ depending on the situation, but estimates often hover around $1,000 to $3,000. 

Estimates aside, the good news is that heat exchangers are often included in the warranty. You’ll want to check the warranty paperwork on your furnace, as while the warranty might not 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 easiest ways to minimize the risk of problems in your furnace overall is through consistent furnace maintenance. Furnaces provide the best possible return on investment when they work efficiently. Contacting a trained professional to check your furnace for old parts, clogs in the air filters and other potential problems can help you avoid getting a big bill later on.  

It’s also beneficial to inspect your furnace filters every few months – it’s encouraged 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 pulling air through a clogged filter makes your entire furnace work longer to accomplish its job. And the harder your furnace works, the more deterioration parts like the heat exchanger will endure.