A furnace is often a background player in your home, ensuring you're warm during the cold winter months. It often won't be noticed until something goes wrong. 

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

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps transition heat from the combustion chamber of your furnace to the air that flows through the air ducts. It typically accomplishes this using coils or tubes that heat the air while functioning as a barrier to keep gas produced in the combustion chamber, called flue gasses, from escaping out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Because of its central role, it isn't surprising that a damaged heat exchanger can be very dangerous. A crack in the heat exchanger can permit dangerous gasses – like carbon monoxide, which can be lethal – to circulate across your home. 

For that reason, do NOT turn on your heater if you think you're dealing with a cracked heat exchanger, as letting it run could make your entire household ill. Contact an HVAC professional as soon as possible if you believe your heating has a cracked heat exchanger that should be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: Cracks in the heat exchanger may cause your furnace to shut off. 
  • Unusual Smells: If the air escaping your furnace has a powerful chemical odor, it may be evidence gas is slipping through cracks in your heat exchanger. These gasses, which may smell like formaldehyde, are a significant warning sign. 
  • Carbon monoxide alarm goes off or you recognize health problems: If a cracked heat exchanger is emitting carbon monoxide in your home, your carbon monoxide alarm should go off or family members could struggle with signs of carbon monoxide poisoning. Complications include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If the alarm goes off or you feel unusually tired, exit the home as soon as you can and then call for help. 
  • Soot: If you see black sooty accumulating near the exterior of your furnace, it’s an indication 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 pro experienced in furnace installation York right away so they can examine your system and, if necessary, perform a furnace heat exchanger replacement. Costs should 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 regularly covered by the warranty. It's a good idea to confirm the warranty paperwork on your furnace, as while the warranty won't always 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 most convenient ways to minimize the risk of problems in your furnace overall is via routine furnace maintenance. Furnaces offer the most benefits when they run efficiently. Calling a certified professional to check your furnace for broken-down parts, clogs in the air filters and other likely problems can help you avoid getting a big bill later on.  

It’s also a good idea 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 dragging air through a clogged filter makes your entire furnace work harder to accomplish its job. And the harder your furnace has to work, the more strain components like the heat exchanger will sustain.