Water-cooled chillers range from 20 to 4,000 tons. These chillers are equipped with Screw type (Helical Rotary), Scroll type or Centrifugal compressors. Reciprocating compressors are not used for chillers due to their high maintenance and high cost. Water cooled chillers consist of compressors, evaporators, and condensers. The common refrigerant for Scroll type compressor is R-410A and for Screw type compressor is R-134a. These chillers efficiency should meet ASHRAE90.1 minimum energy efficiency requirements.