A furnace is often a background player at home, keeping you warm during the cold winter months. It frequently doesn’t get noticed until something goes wrong. 

One cause may be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to learn the signs of a cracked heat exchanger and what you can do if you believe that might be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber of your furnace to the air that flows throughout the ventilation. It typically does this via coils or tubes that warm the air while acting as a barrier to keep the gasses formed in the combustion chamber, called flue gasses, from getting out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Thanks to its central role, it’s no surprise that a cracked heat exchanger can be hazardous. Cracks in the heat exchanger can permit dangerous gasses – such as carbon monoxide, which can be lethal – to circulate across your home. 

For that reason, do NOT run your heater if you suspect there's a crack in the heat exchanger, as letting it run could make your entire household sick. Reach out to an HVAC professional right away if you are worried your heater has a cracked heat exchanger that should be repaired. 

Four Signs of a Cracked Heat Exchanger: 

  • Furnace turns off: A cracked heat exchanger may cause your furnace to shut off. 
  • Unusual Smells: If the air leaving your furnace has an intense chemical odor, it may be an indicator that gasses are slipping through cracks in your heat exchanger. These gasses, which can smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm is triggered or you feel health problems: If a cracked heat exchanger is emitting carbon monoxide inside your home, your carbon monoxide alarm could go off or household members might experience signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling tired. If the alarm goes off or you feel unwell, exit the home as soon as you can and then call for help. 
  • Soot: If you find black sooty collecting around the exterior of your furnace, it’s an indication something may be seriously wrong.

What to Do if Your Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, hire a professional experienced in furnace installation Croydon as soon as possible so they can take a look at 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. 

Fortunately, the good news is that heat exchangers are regularly included in the warranty. You’ll want to confirm the warranty paperwork on your furnace, since while the warranty won't always cover the entire cost of repairs, it still may significantly reduce your bill.  

How to Prevent a Cracked Heat Exchanger in Your Home  

One of the easiest ways to prevent a problem in your furnace overall is via regular furnace maintenance. Furnaces offer the most benefits when they work efficiently. Contacting a trained professional to inspect your furnace for worn-out parts, clogged filters and other potential problems can help you avoid getting a big bill later on.  

It’s also helpful to review 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 longer to do its job. And the harder your furnace has to work, the more strain parts like the heat exchanger will experience.