ABSTRACT
Rooftop units are packaged air handling units. Cooling is mainly accomplished by refrigeration, and the entire refrigeration cycle is within the unit. The refrigeration cycle consists minimally of a compressor, a condenser, an expansion device, and an evaporator. The smaller rooftop units are normally single-stage units, meaning they have only one stage of heating and one compressor. One of the most clever features of a typical, standard rooftop unit, and perhaps also one of the most misunderstood, is the economizer. A temperature controller or thermostat within a zone can command the heating and cooling equipment serving that zone to be in a heating or cooling mode.
