A furnace is usually a background player at home, helping keep you warm across the cold winter months. It often doesn’t get noticed until something breaks down. 

One source could be that your furnace has a cracked heat exchanger. It can potentially be hazardous, so it’s worthwhile to learn the symptoms of a cracked heat exchanger and what to 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 ventilation. It typically accomplishes this through coils or tubes that heat up the air while acting as a barrier to keep the gasses created in the combustion chamber, called flue gasses, from leaking out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Given its important role, it isn't surprising that a cracked heat exchanger can be very dangerous. A crack in the heat exchanger can enable dangerous gasses – such as carbon monoxide, which can be lethal – to circulate throughout your home. 

For obvious reasons, do NOT run your heating if you suspect you're dealing with a cracked heat exchanger, as this could make your entire family ill. Contact an HVAC professional right away if you are worried your heating has a cracked heat exchanger that should be repaired. 

Four Symptoms of a Cracked Heat Exchanger: 

  • Furnace switches off: Cracks in the heat exchanger can cause your furnace to turn off. 
  • Unusual Smells: If the air leaving your furnace has a powerful chemical scent, it could be a sign gasses are seeping through cracks in your heat exchanger. These byproducts, which can smell like formaldehyde, are a major warning sign. 
  • Carbon monoxide alarm is triggered or you recognize symptoms of poisoning: If a cracked heat exchanger is emitting carbon monoxide inside your home, your carbon monoxide alarm could go off or family members may experience signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If your alarm goes off or you feel unwell, get out of the home immediately and then call for help. 
  • Soot: If you see black sooty buildup near the exterior of your furnace, it’s an indication something may be seriously wrong.

What to Do if a Furnace Heat Exchanger is Cracked 

If you suspect your furnace has a cracked heat exchanger, hire a professional experienced in furnace installation Jefferson right away so they can examine your system and, if necessary, perform a furnace heat exchanger replacement. Costs should differ depending on the situation, but estimates often hover around $1,000 to $3,000. 

Fortunately, the good news is that heat exchangers are regularly 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 could significantly reduce your bill.  

How to Avoid a Cracked Heat Exchanger in Your Home  

One of the best ways to minimize the risk of problems in your furnace overall is through routine furnace maintenance. Furnaces work the best when they work efficiently. Calling a trained professional to check your furnace for worn-out parts, clogged filters and other common problems can keep you from getting a big bill later on.  

It’s also helpful 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 drawing air through a clogged filter makes your entire furnace work longer to do its job. And the harder your furnace works, the more strain parts like the heat exchanger will sustain.