We have a campus project that has a unique HVAC system for cooling that reuses return water from a central plant that has already circulated to other campus buildings. Outside air is taken in and cooled first through an energy recovery wheel (using building exhaust), then sent through a pre-cool coil that uses 55F return water from the central plant return loop to cool the air from 105F to 65F. This air is sent through a DX cooling coil of a water source heat pump and further cooled to 48F and then mixed with return air that has been cooled to 58F also using a portion of the 55F return water from the central plant. The water leaving both the return air and outside air pre-cooling water coils is used for heat rejection of the water source heat pump, which returns 75F water to the central plant. We have bounced this off of Carrier HAP and Trane TRACE representatives to no avail. If anyone has any idea how we could possibly model this system, we would greatly appreciate it. Thanks!