What Causes Cracks in a Heat Exchanger?

Tori Klein • February 7, 2023

Furnace Heat Exchanger: How It Works to Warm Your Home

Your heating system uses natural gas as fuel to generate heat. The by-products of gas combustion are routed through the heat exchanger. The metal is heated as the exhaust flows out of the exhaust exit of the furnace.

At the same time, the air is heated by this molten metal. The air ducts in your home are connected to your furnace and send warm air to every room. The heat exchanger will only work once it stays sealed. That's why holes and rifts are so bad for you.

One of the worst problems you might have with your furnace is if the heat exchanger cracks. The heat exchanger in a furnace has two purposes: on one side, it transfers combustion by-products to the flue, and on the other, it distributes heated air throughout the home.

Combustion byproducts like carbon monoxide can enter the home's air supply if the heat exchanger cracks. Almost every result of a furnace's burning is toxic and, in large enough doses, fatal. We have put together this list of possible reasons why heat exchangers break to help solve this problem.

1. Limited Airflow
   Clogged registers reduce the efficiency of your gas furnace. Pressure builds up inside the furnace and creates cracks if the registers are obstructed. Note that a dirty furnace filter or blocked air ducts can also lead to cracks in the heat exchanger.
2. Overheating
   Too much dirt on an air filter can prevent air from passing through the heat exchanger. This causes heat to become trapped in the heat exchanger, putting the part under immense strain. This is a common reason for heat exchanger failure. This is why replacing your air filter once a month is recommended.
3. Your furnace is far too big for your house
   There is a problem with having a furnace that is too big for the house because it will short cycle,' or switch on and off too often. Because of this, the heat exchanger in your furnace goes through more thermal cycling, which causes it to wear out faster and eventually crack.
4. Age
   The heat exchanger in your heating system might crack even with regular maintenance. The metal in your heat exchanger will eventually wear out due to the expansion and contraction that occurs naturally over time. This is occurring after two decades of use is far preferable to replacing your entire furnace after only five years due to avoidable faults.
5. Incomplete combustion
   Combustion troubles in your furnace can also be the result of poor airflow. If the combustion process is incomplete, your gas furnace's burners will need to run hotter and longer. When this extra heat is added to your heat exchanger, the pressure increases, and eventually, it cracks.

Regardless of what caused the crack in the heat exchanger, you must replace it immediately. The alternative is considerably more undesirable, so it's best to give us a call right away. If you think your heat exchanger is broken, don't be afraid to call Best Owner Direct HVAC. We fix furnaces all across Washington County and beyond!

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