What is a Commercial Rooftop Package AC Unit (RTU)? 

In simple terms a package unit means that power goes in one end and conditioned air (AC) blasts out the other. The simplest example of this would be a good old fashioned window unit. If you look to the diagram at the left you can see that the internals of a window unit and commercial package unit follow the same basic principles. Radiator, compressor blower and motor and base and frame. This was how air conditioning was introduced to the general public. Most homes could not have central air conditioning installed since most homes did not have a ventilation system. For those of us who are older we remember that that window ac units represented the simplest times of home air conditioning with a power cord and a window you could change your whole way of living at home. 

A commercial rooftop package unit is similar to window unit except that instead of a window the unit blasts cold (or hot) air down a hole in the roof. That hole is lined with steel (steel liner is called a curb transition). Across the world schools, warehouses, workshops, manufacturing facilities, meeting venues, restaurants, places of worship and theaters functioning in business, entertainment and education outside the home has changed forever.