There have not been major design changes in rooftop units for a while. Most have been around refrigerant changes, scroll compressors, VFD’s for fan control, and economizers. However, we are seeing more and more variable refrigerant flow split units being installed now. 

Design / Replacement considerations & trends.

Variable Refrigerant Flow Units are the trend overseas and have potential over here in new design and retrofit designs.- LG, Mitsubishi & Daiken are a few brands are being installed.

Capacity controlled Compressors and with VFD control compressors and high efficiency condenser

Chillers should be engineered for optimum performance and serviceability, over-sizing is not necessarily a wise choice. For any current performance or future sizing, whether for process cooling or building comfort.