What Are the Causes of Cracks in Furnace Heat Exchangers?

Life Span

• The life span of a regular gas furnace heat exchanger with proper yearly maintenance is about 20 years. Gas package units are outside units, which have a life span of about 10 years because the heat exchanger is subject to the elements outdoors and heats and cools more often.

Rusting

• Furnace heat exchangers that are subject to high levels of moisture will eventually rust. As the aluminized steel cools and heats, the high moisture level causes the metal to rust. After the rust has eaten through the metal, cracks will form in the heat exchanger.

Furnace Filters

• Dirty air filters or filters installed backward will cause the furnace to work harder to get air. When the filter is dirty, minimal air can pass through the filter. After time, the heat exchanger will crack under the pressure of having to work so hard to get the airflow that is needed for the furnace to work. The furnace runs hotter as it tries to get the air it needs and the burners don’t fire correctly, both of which can cause the exchanger material to stress and crack.

Design

• Some heat exchangers have U-shaped bends, which are stretched thin in the design process. The areas where the metal is thin can become cracked over the years from the hot temperatures. Other heat exchangers, such as the kind with a clam shell design, will develop cracks where the metal seams are crimped after years of heating and cooling.