HVAC Journeyman Practice Exam 2025 - Free HVAC Practice Questions and Study Guide

The primary requirement before installing a cooling coil in a duct system with an existing furnace heat exchanger is that air must flow first through the heat exchanger. This is crucial because it ensures that the heating system operates effectively and efficiently. When the air passes through the heat exchanger before reaching the cooling coil, it allows the system to take full advantage of the heating capabilities of the furnace when the heating is needed, and it helps maintain appropriate temperature control in the overall HVAC system.

Proper sequencing of airflow is vital for maintaining comfort and efficiency in the system. If the air flows through the cooling coil first, it can lead to potential issues such as reduced heating efficiency, increased energy consumption, or even damage to the equipment due to improper operation. This requirement ensures that the system can effectively transition between heating and cooling modes, optimizing comfort while safeguarding the integrity of both components.