Premium Efficiency vertical stacked water-source heat pumps offer industry-leading efficiency—as high as 16.6 EER/18.5 EER in ground-loop (geothermal) applications—and a flexible design allowing simple zoning, tenant metering, and building expandability. The units feature the comfort and flexibility of a four-pipe fan-coil system in a cost-effective, two-pipe design and are ideally suited for any multistory building with a consistent floor plan. The pre-engineered piping system reduces installation time and costs and provides for future building expansion.