A central chiller plant uses most of the energy consumed by the total HVAC system within a building. Some interesting conservation opportunities are available to the energy manager or consultant, especially if the building's computerized energy management and control system (EMCS) includes direct digital control (DDC) or (EMCS/DDC). The EMCS/DDC can read the exact position of each cooling coil control, valve and, according to their dictates, reset the control point of the chilled water supply temperature, which is being modulated to maintain the desired cooling supply air temperature. The EMCS/DDC can also monitor the differential pressure (DP) at the end of the chilled water loop and adjust the chilled water pump flow (speed) to just meet the DP required to ensure adequate flow through the cooling coils. This control point can also be reset according to cooling coil valve demand.

This paper will explore these operating modes and identify the expected benefits and some pitfalls to avoid.

Units: Dual