What causes heat exchangers to crack?
Heat exchangers get hot, then cold, then hot again, up to 3 or 4 times an hour during the heating season. These thermal stresses can crack the welds in the heat exchanger causing leaks. What appears to increase the incidence of heat exchanger cracking is overheating. The heat exchanger heats the air in your home, but at the same time, the air in your home cools the heat exchanger. Something as simple as a dirty air filter can reduce the cooling air flow across the heat exchanger which causes it to overheat, which leads to warping, cracking and leaking. Duct work that’s too small or closing too many air vent registers (or even clogged A/C coils) can have a similar effect. It used to be that heat exchangers didn’t leak until they had been in service at least several years, but with many new homes being built with duct work that’s too small and restrictive, it’s not unusual to see heat exchangers developing leaks even in the first season. For this reason, don’t shut off air registers unle
