The Virtual Moveable End Cap (VME) water-to-water heat pump system by Multistack uses a combination of 15-, 20-, 30-, 50- and 70-ton units, to create chiller-heater systems from 15 to 600 tons. Multistack modules use dual independent compressors to ensure redundancy while focusing on energy savings and efficiency. A Multistack VME system is compatible with closed loop and ground loop water source heat pump applications. The significance of the VME is based on Multistack’s proprietary control system that opens and closes valves in between units as demand increases for either chilled or heated water. This design dramatically reduces piping and electrical costs as well as reducing the footprint needed to meet architectural limitations. Set up and installation costs are reduced because the VME units are factory assembled and draw power from the Multistack buss bar system, as standard Multistack modules do.