What factor can contribute to condensation forming in a venting system?

Condensation in a venting system can arise when there is too low of a temperature rise across the heat exchanger. This situation occurs when the heat exchanger is not effectively transferring heat to the fluid or air it is supposed to be heating. As a result, the exhaust gases may remain at a temperature that is not significantly above the dew point of the surrounding air. When the temperature of these gases drops during venting and reaches a point where it can no longer hold moisture, condensation will form. Therefore, a lack of sufficient temperature rise can lead to conditions that promote the accumulation of moisture within the venting system, which can eventually lead to issues such as corrosion or reduced efficiency in the system.

In contrast, while excessive airflow and inadequate vent size can affect performance and efficiency, they do not directly cause condensation. Similarly, the temperature differential between outside air and the vent can influence the efficiency of heat transfer, but it is primarily the inadequate heat transfer resulting in low temperature rise that directly leads to increased moisture and potential condensation in the venting system.