Reciprocating & Scroll


Reciprocating, and to a lesser extent scroll, packaged chillers are the heart of most central systems for medium sized buildings. They consist of one or more reciprocating or scroll compressor-motor assembly, air- or water-cooled condenser (and condenser air fan(s)), insulated liquid cooler, expansion device, interconnecting refrigerant piping, oil and refrigerant charge, control panel and wiring, auxiliaries, and the compressor motor-starter. They are made in both full- and semi-hermetic and open types. They are manufactured, factory assembled and tested, charged, and shipped in one assembly up to about 200 tons capacity. Installation consists of piping supply and return chilled water piping, (and cooling water piping where applicable), power wiring and interconnection of external controls, evacuation and charging when necessary, check-out and startup. Units are also available without any condenser for field piping to a separate remote air-cooled or evaporative condenser.


  • Factory packaged for ease of proper installation
  • Many reliable suppliers, most with a service network of trained technicians or through factory approved service providers
  • Reciprocating models available from many manufacturers in capacities up to 200 tons and larger in incremental steps (i.e. 20, 25, 30, etc)
  • Scroll chillers are available from a lesser number of manufacturers and more limited models (20 to 60 tons - check suppliers)
  • Scroll chillers have improved part load efficiencies
  • Use environmentally acceptable refrigerants
  • Various condensing options available, including air-cooled and for low ambient operation
  • Chillers are relatively easy to operate with their modern controls and designs


  • Reciprocating models: Part load capacity is stepped - cylinder unloading, compressor on/off of multiple compressor units
  • Central plant systems tend to be more costly than unitary systems


Reciprocating and scroll packaged chillers are typically applied in single and multiple units to provide chilled water for air conditioning small to medium sized buildings using central system designs.

Best Applications

High quality installations requiring central chilled/hot water systems to provide temperature and humidity control of multiple spaces.

Retrofit Applications

Many models will fit through a 30 inch door for ease of installation at minimum cost of structural modifications.

Applications to Avoid

Installations where the added expense of a central chilled/hot water system is not justified over that of a unitary equipment type system.

Technology Types (Resource)

Reciprocating compressor packages have been the mainstay of this segment, and many advances and improvements have been made over the years. They are in wide-spread use and trained service technicians are available almost everywhere.

Scroll compressor packages are the latest advancement in positive displacement compressors and indications are they may offer better reliability and improved efficiency. The network of trained service technicians is in the process of development and may not be available in all locations.


Older water cooled chillers are in the 0.82 to 1.0 kW per ton range, while newer high efficiency models range from 0.78 to 0.85 kW per ton at ARI conditions.

Manufacturer Links

Dunham-Bush Inc.
Daikin-McQuay International
The Trane Company
York International Corp.

Links to Related Topics

Centrifugal and Screw
Free Cooling
Natural Gas - Engine Driven