A furnace is often a background player at home, helping keep you warm during the cold winter months. It frequently won't be noticed until something breaks down. 

One root cause might be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to familiarize yourself with 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 of your furnace to the air that moves inside the system. It usually handles this through coils or tubes that warm the air while serving as a barrier to keep gas created 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 damaged heat exchanger can pose a risk. A crack in the heat exchanger can permit dangerous gasses – including carbon monoxide, which can be lethal – to circulate through your home. 

For that reason, do NOT turn on your heating if you believe there's a crack in the heat exchanger, as doing so could make the whole household ill. Contact an HVAC professional as soon as possible if you are worried your heating has a cracked heat exchanger that needs repair. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace shuts off: A crack in your heat exchanger can cause your furnace to switch off. 
  • Unusual Smells: If the air leaving your furnace has a strong chemical smell, 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 is triggered or you feel symptoms of poisoning: If a cracked heat exchanger is emitting carbon monoxide in your home, your carbon monoxide alarm may go off or family members could experience signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If an alarm goes off or you feel unwell, exit the home immediately and then call for help. 
  • Soot: If you spot black sooty collecting 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 believe your furnace has a cracked heat exchanger, hire a pro well versed in furnace installation Croydon as soon as possible so they can take a look at your system and, if necessary, perform a furnace heat exchanger replacement. Costs will differ depending on the situation, but estimates can roughly suggest $1,000 to $3,000. 

However, the good news is that heat exchangers are generally protected by the warranty. You’ll want to review 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 Avoid a Cracked Heat Exchanger in Your Home  

One of the easiest ways to minimize the risk of problems in your furnace overall is with consistent furnace maintenance. Furnaces work the best when they work efficiently. Calling a skilled professional to check your furnace for broken-down parts, clogged filters and other potential 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 encouraged some filters be swapped out 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 pulling air through a clogged filter makes the entire furnace work harder to accomplish its job. And the harder your furnace has to work, the more wear and tear pieces like the heat exchanger will experience.