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

One cause might be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s worthwhile to learn the symptoms of a cracked heat exchanger and what you should do if you suspect that may be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger helps move heat from the combustion chamber inside your furnace to the air that circulates throughout the air ducts. It generally handles this using coils or tubes that warm the air while functioning as a barrier to keep byproducts created in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Given its key role, it’s no surprise that a broken heat exchanger can be very dangerous. Cracks in the heat exchanger can permit dangerous gasses – including carbon monoxide, which can be lethal – to circulate through your home. 

For this reason, never turn on your heater if you suspect you're dealing with a cracked heat exchanger, as doing so could make your entire family ill. Contact an HVAC professional immediately if you believe your heater has a cracked heat exchanger that needs to be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: A crack in your heat exchanger could cause your furnace to turn off. 
  • Odd Smells: If the air coming out of your furnace has a strong chemical odor, it might be an indicator that gas is seeping through cracks in your heat exchanger. These byproducts, which may smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm goes off or you recognize health problems: If a cracked heat exchanger is emitting carbon monoxide into your home, your carbon monoxide alarm may go off or family members might struggle with signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If an alarm goes off or you feel sick, leave the home as soon as you can and then call for help. 
  • Soot: If you find black sooty collecting on the exterior of your furnace, it’s an indication something might be seriously wrong.

What You Can Do if Your Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, call a pro well versed in furnace installation Manassas as soon as possible so they can examine your system and, if required, perform a furnace heat exchanger replacement. Costs often vary depending on the situation, but estimates often hover around $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 may not cover the entire cost of repairs, it can significantly shrink 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 through consistent furnace maintenance. Furnaces offer the most benefits when they run efficiently. Hiring a certified professional to examine your furnace for worn-out parts, clogs in the air filters and other potential problems can keep you from getting a big bill later on.  

It’s also a good idea to review your furnace filters every few months – it’s ideal 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 harder to accomplish its job. And the harder your furnace works, the more strain pieces like the heat exchanger will sustain.