What is the best way to determine if the heat exchanger of a standard furnace has a failure?
• The difficult part of evaluating heat exchangers is the fact that only 15–20% of a standard heat exchanger is visible. The best way to determine if you have a failed heat exchanger is to do the following • Turn the unit on by raising the thermostat. This should cause the atmospheric burners to come on. Look at the flame pattern before the fan comes on. There should be bluish flames with a small amount of orange/yellow at the tips, and they should be erect or vertical. • Look at the burner flames again when the fan comes on. There should be no difference in the flame pattern. If there is, then it suggests that the fan is forcing air from the house side into the path of the flame, and forcing exhaust through a crack or hole in the heat exchanger. This occurs because the fan will pressurize the heat exchanger from the house air side. • Although there are other methods to determine a failure, watching for a distorted flame pattern, while not perfect, is a very dependable method. • Learn
