WaterFurnace International Inc. has released a waterside economizer option to its 2- to 6-ton horizontal and vertical Versatec Base and Versatec Ultra Envision2 Compact and 7- to 25-ton horizontal and vertical Envision XL products. The option allows the use of a building’s interior loop water to provide “free” cooling. The waterside economizer passes air through an internal coil cooled by loop water. The unit contains a water-to-air heat exchanger, a three-way valve and controls that manage the flow of water through the heat exchanger. When cooling is required and the building loop water temperature is below the economizer setpoint, water passes through the economizer. Air is drawn through the cool economizer and the heat pump’s compressor is turned off.