Residential HVAC Installation Practice Exam 2026 - Free HVAC Practice Questions and Study Guide

An extended plenum system is used to prolong the main plenum closer to the farthest supply register. This allows for a more balanced distribution of air throughout the building. Option B, observing a lesson, is incorrect as it does not pertain to HVAC systems. Option C, maintaining a constant pressure, is incorrect as this is typically achieved through a pressure-regulating damper in the main duct. Option D, connecting duct sections, is incorrect as this is not the primary purpose of an extended plenum system. Ultimately, the purpose of an extended plenum system is to provide more even air flow and temperature control in a building.