What is a Water-Cooled Chiller?

A water-cooled chiller is a central cooling device that cools large quantities of water (chilled water), then distributes this chilled water through a network of pipes to Air Handling Units (AHUs) and Fan Coil Units (FCUs) spread throughout the building.

Water-cooled chillers are the optimal choice for buildings exceeding 3,000 m² or with a cooling capacity of 150 tons or more.


Water-cooled chiller with 500RT each — Private hospital project

Types of Water-Cooled Chillers

1. Air-Cooled Chillers

Installed outdoors (rooftop or ground). They condense refrigerant using air fans.

  • Advantage: No cooling tower required — lower operating and maintenance costs
  • Disadvantage: Lower efficiency in hot climates (COP decreases as temperature rises)
  • Suitable range: 20 – 500 tons of refrigeration

2. Water-Cooled Chillers

Use a cooling tower to reject heat. They offer significantly higher efficiency.

  • Advantage: COP up to 7.0 — best for large projects
  • Disadvantage: Requires mechanical room + cooling tower + water treatment
  • Suitable range: 100 – 5,000+ tons of refrigeration

3. Absorption Chillers

Operate using thermal energy (steam or hot water) instead of electricity. Ideal when free waste heat is available.

Energy Efficiency Metrics

Metric Definition Minimum (ASHRAE 90.1)
COP Coefficient of Performance at full load ≥ 5.0 (air-cooled)
EER Energy Efficiency Ratio ≥ 17.0 BTU/W·h
IPLV Integrated Part Load Value ≥ 6.1 (air-cooled)
kW/ton Power consumed per ton of refrigeration ≤ 0.70 kW/ton

Cooling towers connected to central water-cooled chillers — Commercial complex project

Types of Water-Cooled Chiller Compressors

Screw Compressor

Most common in the 100-1,000 ton range. Characterized by high reliability and lower maintenance than reciprocating compressors.

Centrifugal Compressor

For very large projects (500-5,000 tons). Achieves COP efficiency up to 7.5 in the latest magnetic bearing models.

Magnetic Bearing Centrifugal Compressor

The latest technology on the market. Oil-free operation, exceptional efficiency of 0.50 kW/ton, and service life exceeding 25 years.

Chiller Capacity Selection Formula

Chiller Capacity (RT) = (Chilled water flow L/s × ΔT °C × 4.18) ÷ 3.517

Where ΔT = temperature difference between chilled water supply and return (typically 5-7°C in modern designs)

Installation Requirements per ASHRAE

  • Chilled water supply temperature: 6-7°C (industry standard)
  • Chilled water return temperature: 11-12°C
  • System pressure: 10 bar minimum
  • Water flow rate: 0.18 – 0.24 L/s per ton of refrigeration
  • Pipe thermal insulation: Armaflex 25mm thickness for pipes up to 4 inches