RTU stands for "rooftop unit" in HVAC, which is a self-contained unit that provides both heating and air conditioning for certain types of spaces. It is sometimes called a "packaged unit" because all its components are contained in one unit. The components of an RTU include an evaporator section and coil, a condenser section and coil, a compressor, a blower motor and fan, an intake for outside air, economized (if applicable), a heat source (gas, water, or electric heat), a TXV, a liquid line drier, and an exhaust flue.
An RTU is usually a direct-expansion (DX) unitary system, which means that the air is cooled by a refrigerant and can be either fan-cooled or water-cooled. Heat can be produced by gas, electric, or water. The air returns back to the packaged rooftop unit from the space the unit is ventilating, and then moves through filters and a cooling coil, which chills air by running it over refrigerant. The air then flows through a blower, leaving it conditioned and ready for the space.
RTUs are commonly used for large, open spaces such as warehouses, large stores, and shopping centers. Single-story buildings are best suited, since the conditioned air doesnt have to travel very far to the space. However, RTUs can be used in multi-story buildings as long as they dont exceed 10 stories, and there is accessible space on the roof and ductwork in place.
The advantages of RTUs include energy efficiency, space-saving, and cheaper installation. All the components have been configured under optimal conditions in the factory, making RTUs extremely efficient. All the components are housed on the roof, so no indoor space is lost, which is particularly advantageous for retail outlets where every inch of square footage is valuable. The disadvantages of RTUs include limited application and exposure. RTUs are not suitable for all types of buildings, and they require a flat roof space with easy access. They will not work efficiently on buildings over ten stories high. If an RTU is sitting up on the roof where you can neither see nor hear it, you could easily forget about regular maintenance until it is too late.
