Which category of vented appliance operates with positive vent static pressure while avoiding excessive condensate?

The category of vented appliance that operates with positive vent static pressure while avoiding excessive condensate is correctly identified as Category 3. This category is designed for appliances that generate flue gases with moderate combustion temperatures.

A key characteristic of Category 3 appliances is that they typically use non-condensing venting systems, which means they can maintain a positive pressure within the vent. This positive static pressure is essential for ensuring that flue gases are efficiently expelled from the appliance without allowing the gases to condense within the vent system. By preventing condensate buildup, these appliances help maintain the integrity and efficiency of the venting system, as condensation can lead to corrosive damage and operational problems.

In contrast, other categories exhibit different venting characteristics. Category 1 appliances operate with a negative vent static pressure, which can lead to issues with flue gas drafts. Category 2 appliances are designed to allow for some condensation but do not operate at a positive pressure. Category 4 appliances utilize condensing technology, but they also do so under specific conditions that do not align with the definition of avoiding excessive condensate in the way Category 3 does.

Thus, recognizing the significance of vent static pressure and the implications of condensate management is crucial when identifying the