What is the function of a bypass damper on an air heater?

The function of a bypass damper on an air heater is primarily to prevent moisture from collecting at low firing rates. When an air heater is operating at lower capacities, there is a risk that the temperature may drop below the point where moisture can condense. This condensation can lead to water accumulation, which can harm the system by promoting corrosion, reducing efficiency, and potentially damaging components over time.

By using a bypass damper, the system can redirect a portion of the airflow around the air heater, maintaining higher temperatures and ensuring that the air entering the system remains above the dew point. This helps to keep moisture in the air in vapor form instead of allowing it to condense, thus protecting the equipment and enhancing overall reliability.

While other options address various concerns, they do not accurately describe the primary function of a bypass damper in the context of air heaters. For instance, while increasing air temperature or enhancing combustion efficiency are important goals in a heating system, these are not specific roles of the bypass damper during low firing rates. Similarly, reducing airflow during maintenance is relevant for overall system management but does not directly pertain to the functions of a bypass damper.