G2 Gas Fitter Practice Exam

An 85% efficient furnace with non-positive vent pressure is classified as which category?

1. Category 1

2. Category 2

3. Category 3

4. Category 4

The correct answer is: Category 2

A furnace’s efficiency and venting characteristics are key factors in determining its category classification. In this case, a furnace with an efficiency rating of 85% and non-positive vent pressure would indeed fall under Category 2. Category 2 appliances are those that operate with a venting system designed to transport flue gases, where the flue gas temperature may not exceed the condensation point, and non-positive pressure indicates that the venting system is not pressurized. This means that the appliance is not capable of venting flue gases under positive pressure, which is a significant characteristic of Category 2 systems. In contrast, Category 1 appliances are typically less efficient and vent flue gases without the sophistication found in higher categories. Category 3 appliances must be able to vent positive pressure and are generally more efficient than Category 1, while Category 4 appliances are designed to operate with condensing and positive vent systems, generally at efficiencies above 90%. Thus, the classification of an 85% efficient furnace with non-positive vent pressure as Category 2 aligns perfectly with the operational characteristics and the efficiency standards specified for such appliances.