In a single chilled water pump with VFD what are the by pass valves used and how are they balanced according to the load?

In single VFD chilled water pump the Motorised Butterfly valves are used to maintain minimum flow across chilled water pumps.The by pass of chilled water from supply chilled water header to returnly chilled water header to ensure the chilled water pump does not trips during night time when load is not lesser not sufficient enough and also when TWO WAY-ON -OFF valves are used during less load all two way valves will be closed developing back pressure in the chilled water system -Pumps may trip on high Pressure sensed by differential Pressure Transmitter across kept between Supply and Return header of the pump.

The balance of the system is created with above described Motorised Butterfly valve ensures no tripping of the chilled water pumps even at lower or lesser cooling loads.Also the last AHU of the chilled water pipe header is provided with3-Way valve instead2-Way Valve ensures balancing smooth operation of the chilled water pump.