Configuration for modular rooftop air conditioning system

A bus rooftop air conditioning system is made up of one or more self-contained modules having one or more evaporator sections and one or more condenser sections, with each extending transversely across the width of the bus, and with the evaporator sections fluidly communicating with both a common return air opening and a common supply air opening of the bus. The modules may be of a single unit configuration with a single condenser section and a single evaporator section or they may be of a double unit configuration having two condenser sections and two evaporator sections. The total capacity requirements are met by combining the use of single units and double unit configuration, with each of the evaporator sections communicating with a single return air opening and a single supply air opening in a bus.