ESCO Air Conditioning Practice Exam 2026 - Free AC Certification Practice Questions and Study Guide

Subcooling the liquid refrigerant before it reaches the metering device keeps it fully condensed and well below its condensation temperature. This means the expansion device meters mostly liquid, with minimal flashing into vapor as it expands. Because more liquid refrigerant reaches the evaporator and can absorb heat, the cycle delivers cooling more efficiently, so the compressor doesn’t have to work as hard for the same cooling effect. In other words, keeping the incoming liquid subcooled improves the compression cycle’s efficiency, which is why this practice boosts overall system efficiency.