Chillers

Summary

Chillers remove heat from water circulated to air handler and fan coil coils, rejecting it outdoors through air-cooled condenser coils or through condenser water and cooling towers in water-cooled plants. They anchor central cooling plants, so plant type, location, noise, structural loads, cooling tower space, and efficiency at part load must be settled early.

Cols

Image

Air-cooled chiller: outdoor unit rejecting heat to air with condenser fans
Water-cooled chiller: indoor unit rejecting heat to condenser water and cooling towers
Compressor types: scroll (small), screw (medium), centrifugal (large), magnetic-bearing oil-free centrifugal
kW/ton: water-cooled efficiency; lower is better
EER: air-cooled efficiency; higher is better
IPLV / NPLV: integrated part-load value at standard or project conditions
Heat recovery chiller / heat pump chiller: machine that produces hot water from rejected heat
Primary / variable primary flow: chilled water pumping arrangements
Cooling tower: evaporative heat rejection for water-cooled plants

Standards

Ratings

Water-cooled chillers rated in kW/ton and air-cooled chillers in EER at AHRI 550/590 conditions; IPLV reported for part load
Example incentive thresholds (2026): water-cooled centrifugal 150 to 300 tons at 0.580 kW/ton full load and 0.380 kW/ton IPLV; air-cooled under 150 tons at 16.59 EER IPLV
Minimum efficiencies set by the energy code

Test standards

AHRI 550/590: chiller performance ratings
ASHRAE 15 and 34: refrigerant safety and classification, including machinery rooms
ASHRAE 90.1 / IECC: minimum efficiency

Components

Compressors and evaporator: chilled water heat exchange
Condenser: air-cooled coils or water-cooled shell-and-tube
Controls: chiller and plant controls
Pumps, cooling towers, and piping: plant equipment
Refrigerant monitoring and ventilation: machinery room safety

Detailing

Provide machinery rooms with refrigerant detection, ventilation, and alarms as required
Plan air-cooled chiller locations for airflow clearances, noise, and structural support
Allow tube-pull space for water-cooled chillers
Locate cooling towers away from intakes and provide water treatment
Consider heat recovery chillers where simultaneous heating and cooling exists

Uses

Specific uses

Office towers and campuses
Hospitals and laboratories
Data centers
Universities with district plants
Large retail and mixed-use projects

Pros and cons

Pros

Efficient cooling for large loads
Central plant serves many buildings or zones
Heat recovery chillers support electrification
Long equipment life

Cons

Large plant rooms, towers, and piping
Water and chemical use for water-cooled plants
High first cost and specialized maintenance
Refrigerant safety and machinery room requirements

Manufacturing and cost

Construction

Chillers set by crane or rigged into plant rooms; piped, wired, and started up by factory technicians

Main manufacturers and suppliers

Trade associations: AHRI and ASHRAE.

Sources

New Hampshire Saves: 2026 chiller incentives (efficiency thresholds), https://nhsaves.com/wp-content/uploads/2026/01/2026_ChillerIncentives_NewEquipment_1.20.26.pdf
Aircondlounge: chiller efficiency kW/ton, COP, EER, IPLV, https://aircondlounge.com/chiller-efficiency-calculation-kw-ton-cop-eer-iplv-nplv/
CSE Magazine: calculating chiller selection, https://www.csemag.com/?p=12586
Sweets: Division 23 HVAC (23 64 00), https://sweets.construction.com/BrowseByDivision/Heating, Ventilating, and Air-Conditioning (HVAC)
Wikimedia Commons: Air-Cooled Chiller System Diagram.jpg, by Ridvan Ozbay (CC0), https://commons.wikimedia.org/wiki/File:Air-Cooled_Chiller_System_Diagram.jpg