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

One root cause may be that your furnace has a cracked heat exchanger. It’s a potentially dangerous issue, so it’s worthwhile to learn the evidence of a cracked heat exchanger and what to do if you are worried that may be the problem.  

What Is a Heat Exchanger in a Furnace? 

A heat exchanger transfers heat from the combustion chamber in your furnace to the air that moves throughout the air ducts. It typically does this via coils or tubes that heat up the air while acting as a barrier to keep gas produced in the combustion chamber, called flue gasses, from escaping out into your home.  

Is a Cracked Heat Exchanger Dangerous? 

Thanks to its important role, it’s no surprise that a damaged heat exchanger can be hazardous. Cracks in the heat exchanger can enable dangerous gasses – like carbon monoxide, which can be lethal – to be distributed through your home. 

For this reason, do NOT use your heater if you suspect there's a crack in the heat exchanger, as letting it run could make your entire family ill. Call an HVAC professional as soon as possible if you are worried your furnace has a cracked heat exchanger that needs repair. 

Four Warning Signs of a Cracked Heat Exchanger: 

  • Furnace turns off: A cracked heat exchanger could cause your furnace to switch off. 
  • Odd Smells: If the air coming out of your furnace has an intense chemical scent, it could be an indicator that gasses are slipping through cracks in your heat exchanger. These byproducts, which may smell like formaldehyde, are a significant warning sign. 
  • Carbon monoxide alarm is triggered or you feel poisoning symptoms: If a cracked heat exchanger is releasing carbon monoxide into your home, your carbon monoxide alarm should go off or household members might struggle with signs of carbon monoxide poisoning. Side effects include headaches, dizziness, weakness, nausea, vomiting or feeling sleepy. If an alarm goes off or you feel sick, exit the home immediately and then call for help. 
  • Soot: If you notice black sooty accumulating near the exterior of your furnace, it’s another sign something might be seriously wrong.

What to Do if the Furnace Heat Exchanger is Cracked 

If you believe your furnace has a cracked heat exchanger, call a pro experienced in furnace installation Milwaukee right away so they can take a look at your system and, if needed, start a furnace heat exchanger replacement. Costs often fluctuate depending on the situation, but estimates often hover around $1,000 to $3,000. 

Estimates aside, the good news is that heat exchangers are generally protected by the warranty. It's a good idea to check the warranty paperwork on your furnace, since while the warranty may not cover the entire cost of repairs, it can significantly shrink 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 via regular furnace maintenance. Furnaces provide the best possible return on investment when they operate efficiently. Hiring a trained professional to check your furnace for broken-down parts, clogs in the air filters and other likely problems can keep you from 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 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 dragging air through a clogged filter makes the entire furnace work more vigorously to complete its job. And the harder your furnace needs to run, the more deterioration parts like the heat exchanger will experience.