Which category of venting system is characterized by operating at less than 140°F above the flue gas dewpoint?

The correct answer is associated with Category 2 venting systems, which are specifically designed to operate with flue gases that have a temperature less than 140°F above the dew point of the flue gases. This is significant because a lower temperature within this category helps to reduce heat losses and increases overall efficiency.

In a Category 2 venting system, the venting employs a non-positive, non-condensing operation which facilitates the safe removal of flue gases while maintaining a lower internal temperature. This lower operating temperature is critical in ensuring that the venting system can efficiently handle flue gases without significant heat loss, thereby enhancing comfort and energy savings.

The definition and operational parameters of Category 2 are distinct from those of the other category options. Category 1 typically refers to non-condensing systems operating at higher temperatures, allowing for positive pressure venting. Conversely, Category 3 systems are categorized as positive pressure and operate with more stringent requirements for flue gas temperature. Category 4 systems, on the other hand, are condensing systems that operate with flue gas temperatures below the dew point.

Thus, understanding the characteristics of Category 2 in relation to its flue gas temperature helps clarify why this category is identified for operational temperatures