The TES tank connects to the CHWS and CHWR headers similar to above; however, the water must always be pumped from the atmospheric pressure of the TES tank into higher-pressure chilled water headers.
Maintain positive differential pressure between the CHWS and CHWR headers.
Therefore, for this installation, as result of the height of the chilled water tank, the connection of the tank into the system and the resulting chilled water system pressures the pumps are required to operate simultaneously (at least in some operating conditions) on both the CHWS and CHWR.
Using simultaneous dual pumping of CHWS and CHWR on a TES tank had been tried previously on other TES systems, but in each instance we studied, it was not successful.
The system in Figure 2 shows the TES tank, the CHWS and CHWR pumps as well as the chilled water production facilities at the existing central plant and the future east chiller plant.
This solution has the CHWS pump being controlled either based on a fixed flow rate selected by the operator, or controlled by the differential pressure out in the chilled water system.