What is one indication of a potential crack or hole in the heat exchanger?

An irregular flame pattern when the blower starts is indeed an important indication of a potential crack or hole in the heat exchanger. This occurs because a compromised heat exchanger can cause incomplete combustion or the mixing of combustion gases with incoming air. When there is a crack or a hole, the flame may appear uneven or flickering, indicating a disruption in the normal combustion process.

For example, if the heat exchanger is leaking, the air-fuel mixture can become unbalanced, leading to variations in flame characteristics. This irregularity can also produce a safety hazard since it may indicate that harmful gases could be escaping into the living space. Therefore, observing an irregular flame pattern should prompt a thorough inspection of the heat exchanger.

While the other options may relate to various operational issues with heating systems, they do not specifically indicate a crack or hole in the heat exchanger. Short cycling can be related to a variety of factors, such as thermostat issues or over-sizing of heating equipment, and a clogged filter typically results in reduced airflow rather than indicating a breach in the heat exchanger. Staining in the combustion area can suggest other problems, but it’s not as direct an indication of physical damage to the heat exchanger as an irregular flame pattern is.