A packaged rooftop unit contains all air conditioning component,the evaporator coil, fan, compressor, and condense are all within one cabinet, it’s considered a packaged unit. Rooftop units that also provide heating often contain a gas heat exchanger downstream from the evaporator fan. In heating mode, return air is discharged into the heater and blows over gas-fired coils. A fan then sends newly heated supply air back into the building.
Package unit is set apart from a split system, which is the common type of air conditioner/heat pump found in houses. A split system has an outdoor cabinet and an indoor cabinet with different sets of components. The outdoor cabinet has a compressor, fan, and a condenser coil; the indoor cabinet has a blower, dampers, air handler, and evaporator coil, and hooks into the ventilation system.