Variable Speed Primary Headered Chilled Water System
In a variable speed configuration, the appropriate number of pumps needed to supply the required chilled water flow are turned on. The pump speeds are modulated to maintain the differential pressure (dP) setpoint. As an option, the setpoint can be reset by either a second sensor that measures differential pressure near the end of the building’s chilled water loop, or by the valve positions of the main chilled water coils in the building. As the number of pumps and the speed of the pumps changes, chilled water flow through the chillers and building changes.
Variable Speed Primary Dedicated Chilled Water System
In a variable speed
dedicated chilled water pump configuration, the pumps are interlocked to their
dedicated chillers and the pumps modulate to control the building dP to the dP
setpoint. As pump speed changes, the water flow through the chillers and
building also changes. As an option, the setpoint can be reset by either a
second sensor that measures dP near the end of the building’s chilled water
loop, or by the valve positions of the main chilled water coils in the
building. A bypass valve is available for chilled water minimum flow control.
Note: If primary pumps are variable speed, you cannot have a secondary
chilled water loop.