To provide cooling, chilled water loops are installed in a coil and a mixture of outdoor and "return" air is blown across. (This system can also use hot water coils (from boilers) to provide heating.) The primary energy user in a chilled water system is the chiller's compressor bank. Baseline systems are often reciprocating compressors-while scroll, screw, or centrifugal compressors offer higher efficiency options, depending upon the size and application. You can also improve the efficiency of chilled water production by reducing condenser water temperature, raising chilled water temperature, varying chilled water flow and condenser fan speed, and installing water-side economizers on the cooling tower systems. Increased efficiencies can be obtained by using variable speed control on chilled water pumps and ventilation fans, and the use of NEMA Premium^TM fan motors.