What is the most common reason for gas-fired furnace heat exchanger failure?

The most common reason for gas-fired furnace heat exchanger failure is rust and metal fatigue. Over time, the materials used in heat exchangers can degrade due to the constant cycling of heat and exposure to combustion byproducts, which can lead to corrosion. This process often starts with minor surface rust, which can gradually worsen, resulting in small holes or cracks that compromise the integrity of the heat exchanger.

Additionally, metal fatigue occurs as the metal expands and contracts with each heating cycle. Repeated thermal stress can weaken the material, making it more susceptible to failure. Given that heat exchangers operate at high temperatures and under continuous use, these factors combined create an environment where rust and metal fatigue are prevalent, ultimately leading to potential leaks of combustion gases into the living space, which poses health risks.

Other factors like low temperatures, lack of use, or improper gas pressure can affect a furnace's operation, but they are not as significant in relation to heat exchanger failure as rust and metal fatigue. For instance, low temperatures may result in less efficient operation but are unlikely to directly cause physical breakdown. Similarly, lack of use might lead to problems such as dust buildup or mechanical wear, but again, they do not primarily influence the integrity of the heat exchanger itself. Impro