Air Handing Unit (AHU)

A Water Source Heat Pump (WSHP) is for heating or cooling outside and return mixed air, using geothermal water as its source. During the summer, the WSHP works as chiller, where the cool water from geothermal system acts as a source of cooling for the condenser. During the winter, it works as a heat pump, where the hot geothermal water acts as heating source for the evaporator. In both conditions, the refrigerant (Glycol) completes heat transfer in the primary coils of the AHU.

After passing through the ERC, the mixed air enters the Tricoil Unit, which is composed of three coils. The first, second and third coils are called the pre-cooling coil, primary coil and the downstream third coil. To understand how the system works, consider an instance in the summer. In this situation, some of the sensible heat in the mixed air is picked up in the first coil, which reduces the cooling load. The mixed air then goes through the second coil, where it undergoes refrigeration and dehumidification processes, becoming cold and dry supply air. Finally, in the downstream third coil, the cold, dry supply air is warmed up a bit for comfort, but stays nice and dry. The coolness picked up by the reheat coil in this process is then transferred back to the pre-cooling coil to restart the sequence.