Gas Heat ESCO Practice Exam

Where should the transition to a larger vent pipe size be made when venting Category I furnaces?

1. At the furnace connection

2. At the roof peak

3. At the vent cap

4. Midway along the vent run

The correct answer is: At the furnace connection

The correct answer is that the transition to a larger vent pipe size should be made at the furnace connection. This is important because when venting Category I furnaces, which operate with a negative pressure within a venting system, the connection point is critical for ensuring that the venting system functions properly. Making the transition at the furnace connection allows for optimal flow of combustion gases, minimizing the risk of backdrafts and ensuring that all exhaust is effectively expelled from the home. It also helps maintain the necessary draft requirements for safe operation, as the gases begin to rise and expand when exiting the furnace. Transitioning at other points, such as the roof peak, vent cap, or midway along the vent run, may not provide the same efficiency and could potentially disrupt the necessary airflow, leading to performance issues or safety hazards. Therefore, the furnace connection is the ideal location for this adjustment.