The Chilled Water and Hot Water Building Differential Pressure Setpoint Calculation - Chilled Water and Hot Water Pump Speed Control

Abstract

More and more variable frequency devices (VFD) are being installed on the chilled water and hot water pumps on the TAMU campus. Those pump speeds are varied to maintain chilled water or hot water building deferential pressure (DP) or return temperature or flow rate at their setpoints. The chilled water and hot water DP setpoint or return temperature setpoint or flow rate setpoint was a constant value or reset based on outside air temperature. In some buildings, the chilled water and hot water DP setpoints were reset based on flow rate, but in many instances those setpoint schedules were either too low to maintain enough building DP requirement or too high and consumed excess energy. The building DP reset schedule based on flow rate is studied and compared with the other pump speed control methods. Because the building DP setpoint based on flow rate method is achieved by tracking the load change, it saves energy than the other methods. In this paper its calculation procedure is generated and the example of the building DP calculation is given.