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

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

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber inside your furnace to the air that moves inside the system. It typically accomplishes this using coils or tubes that warm the air while acting as a barrier to keep byproducts formed 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 shouldn't come as a surprise that a cracked heat exchanger can be hazardous. Cracks in the heat exchanger can enable dangerous gasses – like carbon monoxide, which can be lethal – to flow throughout your home. 

For that reason, don't ever turn on your heating if you suspect it has a cracked heat exchanger, as letting it run could make the entire household sick. 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 turns off: A crack in your heat exchanger could cause your furnace to shut off. 
  • Strange Smells: If the air leaving your furnace has a powerful chemical scent, it might be an indicator that gasses are slipping through cracks in your heat exchanger. These byproducts, which will often smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm is triggered or you notice poisoning symptoms: If a cracked heat exchanger is relieving carbon monoxide in your home, your carbon monoxide alarm should go off or household members could experience signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If the alarm goes off or you feel unusually tired, exit the home right away and then call for help. 
  • Soot: If you spot black sooty buildup around the exterior of your furnace, it’s more evidence something could be seriously wrong.

What You Can Do if the Furnace Heat Exchanger is Cracked 

If you worry your furnace has a cracked heat exchanger, call a professional with extensive experience in furnace installation Huntsville right away so they can inspect your system and, if required, 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 often protected 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 could significantly lower your bill.  

How to Avoid 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. Contacting a skilled professional to examine your furnace for old parts, clogged 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 encouraged 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 your entire furnace work harder to complete its job. And the harder your furnace has to work, the more strain parts like the heat exchanger will sustain.