A Carrier RoofRoof Top Unit (RTU) is a type of HVAC system that is installed on the roof of a building. It is typically used in commercial and industrial applications and is designed to provide heating, cooling, and ventilation to the interior of the building. The RTU is composed of several components, including an air handler, evaporator coil, condenser coil, and fan. The air handler is responsible for moving air through the system, while the evaporator and condenser coils are responsible for cooling and heating the air. The fan is responsible for distributing the air throughout the building. The RTU is an efficient and cost-effective way to provide heating, cooling, and ventilation to a building. It is also relatively easy to install and maintain, making it a popular choice for many commercial and industrial applications.