A furnace is usually a background player in your home, helping keep you warm during the cold winter months. It frequently isn't noticed until a malfunction appears. 

One root cause could be that your furnace has a cracked heat exchanger. It can be a safety risk, so it’s important to know the symptoms of a cracked heat exchanger and what you should do if you suspect 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 flows through the air ducts. It generally accomplishes this through coils or tubes that heat the air while functioning as a barrier to keep gas formed in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Thanks to its central role, it’s no surprise that a broken heat exchanger can be very dangerous. A damaged heat exchanger can permit dangerous gasses – such as carbon monoxide, which can be lethal – to circulate across your home. 

For this reason, don't ever run your furnace if you suspect it has a cracked heat exchanger, as this could make the whole household sick. Call an HVAC professional as soon as possible 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 could cause your furnace to turn off. 
  • Odd Smells: If the air escaping your furnace has an intense chemical smell, it may be an indicator that 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 initiates or you notice symptoms of poisoning: If a cracked heat exchanger is releasing carbon monoxide into your home, your carbon monoxide alarm could go off or family members might experience signs of carbon monoxide poisoning. Symptoms include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If an alarm goes off or you feel unusually tired, exit the home immediately and then call for help. 
  • Soot: If you notice black sooty collecting on the exterior of your furnace, it’s more evidence something may be seriously wrong.

What to Do if a Furnace Heat Exchanger is Cracked 

If you worry your furnace has a cracked heat exchanger, contact a professional well versed in furnace installation Manassas right away so they can examine your system and, if required, handle a furnace heat exchanger replacement. Costs will differ depending on the situation, but estimates can roughly suggest $1,000 to $3,000. 

Estimates aside, the good news is that heat exchangers are regularly protected by the warranty. You should confirm the warranty paperwork on your furnace, because while the warranty may not 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 easiest ways to avoid problems in your furnace overall is via routine furnace maintenance. Furnaces offer the most benefits when they run efficiently. Contacting a skilled professional to examine your furnace for worn-out parts, clogs in the air filters and other potential problems can help you avoid getting a big bill later on.  

It’s also beneficial to inspect your furnace filters every few months – it’s recommended some filters be swapped out 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 drawing air through a clogged filter makes your entire furnace work more vigorously to complete its job. And the harder your furnace works, the more strain pieces like the heat exchanger will sustain.