The control of variable-speed pumps on hot- and chilled systems must be based upon a hydraulic analysis of the water system. This hydraulic analysis enables the control manufacturer to select and program the variable-speed and pump addition and subtraction controls to achieve the maximum system (wire-to-water) efficiency. Unit responsibility is secured by requiring the control manufacturer to furnish the variable-speed drives. Control of these pumps is achieved through the use of differential pressure transmitters and continuous interrogation of them. This eliminates system hunting, continuous variation in pump speed, and inefficient pump operation.

KEYWORDS: variable speed motors, pumps, water pumps, controls, efficiency, hot water supply, chilled water supply, optimisation.