Unit 6 — Refrigeration System Components
Section 5 — Compressor Performance Metrics
Quantifying how a compressor performs — how much refrigerant it moves,
how efficiently it uses energy, and how its capacity is measured and rated —
is essential for equipment selection, system diagnostics, and regulatory compliance.
This section covers compression ratio, volumetric efficiency, capacity units, and
the efficiency indices used throughout the HVAC/R industry.
5.0.3 — Why Performance Metrics Matter
A compressor is the most expensive component in any refrigeration system, and most
compressor failures can be traced to operating conditions that fall outside acceptable
performance ranges. Understanding these metrics lets a technician recognize a system
in distress before it fails, not after.
Compression ratio tells you how hard the compressor is working. Volumetric efficiency
tells you how effectively it is pumping. Capacity tells you how much useful work the
system is delivering. COP and EER tell you how efficiently it is delivering that work.
Together, these five metrics form a complete picture of compressor health and system
performance that cannot be obtained from pressures and temperatures alone.
These metrics also connect directly to regulatory compliance. Canada’s Energy
Efficiency Regulations and the Ontario Building Code both reference EER and SEER
minimum thresholds. A technician who can read a nameplate, interpret the rating
conditions, and estimate actual field efficiency from measured values is equipped
to support both performance diagnostics and compliance verification.