The rooftop package, or packaged unit, is actually a combination of a chiller and an air handling unit in an integrated system. Rooftop packages perform heating, cooling, filtration, and humidity control of the air. The internal components of the unit include an air-cooled chiller, a refrigerant coil, a hot water coil, a fan, a filter, and humidity control equipment. In cooling mode, the air-cooled compressor chiller operates and sends the refrigerant to the refrigerant coil (evaporator), and the fan, by rotating and forcing air over the coil, lowers the air temperature. In heating mode, hot water must be sent from the boiler or wall-mounted packaged unit to the hot water coil, and the fan, by rotating, increases the air temperature. The rooftop package also has three air channels: supply air, return air, and fresh air.

Rooftop packages are installed in open spaces, often on rooftops, and typically have three vents (fresh air intake, return air vent, and conditioned air outlet from the unit to various parts of the building). Fresh air mixes with return air (recirculated), and after being heated or cooled and passing through the filters installed in the unit, it exits through the unit’s outlet and enters the building via ductwork. Due to the use of a compression refrigeration cycle (similar to chillers, air conditioners, etc.) in this device, its cooling is very comfortable, and due to the use of hot water from the boiler or packaged unit, its heating is also very pleasant.