How Commercial Chillers Work | Refrigeration Cycle Guide

The Basic Refrigeration Cycle

A commercial chiller operates on the vapor-compression refrigeration cycle. The four main components are:

Evaporator: Chilled water flows through the evaporator tubes. Refrigerant inside absorbs heat from the water, lowering the water temperature. The refrigerant evaporates from liquid to vapor.
Compressor: The compressor draws in low-pressure refrigerant vapor and compresses it to high pressure, raising its temperature. This is the primary energy-consuming component.
Condenser: High-pressure hot refrigerant vapor flows to the condenser where heat is rejected. In water-cooled chillers, cooling tower water absorbs the heat. In air-cooled chillers, fans blow air over condenser coils. The refrigerant condenses back to liquid.
Expansion Valve: The high-pressure liquid refrigerant passes through an expansion valve (TXV or EEV), which drops the pressure and temperature, sending cold liquid back to the evaporator to repeat the cycle.

Measurement	Typical Range	What It Tells You
Chilled Water Supply Temp	42-45 F (5.6-7.2 C)	Cooling output temperature
Chilled Water Return Temp	55-58 F (12.8-14.4 C)	Building cooling load
Condenser Water Supply	85 F (29.4 C)	Cooling tower output
Condenser Water Return	95 F (35 C)	Heat rejected from chiller
Suction Pressure	Varies by refrigerant	Evaporator pressure / low side
Discharge Pressure	Varies by refrigerant	Condenser pressure / high side
Superheat	8-12 F (4.4-6.7 C)	TXV operation / compressor protection
Subcooling	8-12 F (4.4-6.7 C)	Refrigerant charge level

Type	Capacity Range	Typical Applications
Reciprocating	10-150 tons	Small commercial, older units
Scroll	10-100 tons	Small to medium commercial
Screw	50-1000+ tons	Medium to large commercial
Centrifugal	150-5000+ tons	Large commercial, campus, data centers