Air Conditioning Certification (A-02) Practice Exam 2025 – Comprehensive Prep Resource

A sight glass is typically found in the liquid line, specifically ahead of the metering device, which is used to visually check the presence of liquid refrigerant and its condition. The primary purpose of the sight glass is to indicate whether the liquid refrigerant is fully saturated, ensuring that the system is functioning properly. When the refrigerant passes through the liquid line, the sight glass allows technicians to observe the flow and confirm that the refrigerant has not vaporized prematurely before reaching the expansion device where metering occurs.

This position is critical since the liquid refrigerant must be in the correct state before it enters the metering device, which regulates the flow to the evaporator coil. If vapor is detected in the sight glass, it indicates potential issues within the system, such as low refrigerant levels or improper flow, which could lead to inefficiencies or compressor damage if not addressed. Placing the sight glass in this location helps ensure optimal performance and easy monitoring of the refrigeration system.