Quite often, design engineers choose decentralized HVAC systems because of first-cost benefit, packaged equipment, simplicity of design, and the repetitiveness of the installation, to mention just a few of the features. One should read chapter two of the 2016ASHRAEHVACSystemsandEquipment Handbook for a more detailed discussion on decentralized HVAC.
That said, decentralized equipment includes packaged units with self-contained refrigeration, remote air-cooled and water-cooled condensing units, heat pump units, VRF units, specialty units (e.g., computer room packaged units) and/or rooftop units. Included in the decentralization design can be fan coil units and other terminal HVAC equipment distributed throughout the building.