What does a sudden increase in stack temperature typically indicate?

A sudden increase in stack temperature typically indicates a problem within the boiler system that can disrupt normal operations. When stack temperatures rise unexpectedly, it often signifies that the flow of combustion gases is impeded or that heat is not being transferred effectively. This situation can occur if components like baffles, which are designed to direct airflow and improve heat transfer, are damaged or missing. Broken baffles can lead to improper gas flow patterns, allowing gases to exit without fully utilizing the heat available, resulting in higher temperatures in the stack.

In contrast, an efficient combustion process would usually be indicated by stable and appropriate stack temperatures, showcasing effective heat exchange and energy use. A decrease in fuel efficiency may be a consequence of temperature changes, but it doesn't directly correlate to the immediate increase in stack temperature. Similarly, an impending failure of the boiler can lead to various warnings, but a sudden spike in temperature primarily suggests an issue like broken baffles affecting the flow and heating dynamics within the system.