Daikin WGZ030DW Installation, Operation And Maintenance Manual page 9

Figure 3: Typical Evaporator Field Water Piping (WGZ030 - WGZ130)
Figure 4: Typical Evaporator Field Water Piping (WGZ150 - WGZ200)
For normal comfort cooling applications where the cooling load
changes relatively slowly, a minimum system volume of two
to three minutes times the flow rate (GPM) is recommended.
For example, if the design chiller flow rate is 120 gpm, we
recommend a system volume of 240 to 360 gallons.
For process applications where the cooling load can change
rapidly, additional system water volume is needed. A process
example would be the quenching of hot metal objects. The load
would be very stable until the hot metal is dipped into the water
tank. Then, the load would increase drastically.
Since there are many other factors that can influence
performance, systems can successfully operate below these
suggestions. But as the water volume decreases below these
guidelines, the possibility of system instability increases.
www.DaikinApplied.com
Variable Chilled Water Flow
Reducing chilled water flow in proportion to load can reduce
total system power consumption. Certain restrictions apply to
the amount and rate of flow change. The rate of flow change
should be a maximum of 10 percent of the change, per minute.
For example, if the maximum design flow is 200 gpm and it will
be reduced to a flow of 140 gpm, the change in flow is 60 gpm.
Ten percent of 200 gpm equals 20 gpm change per minute, or
a minimum of three minutes to go from maximum to desired
flow. Do not reduce flow lower than the part load minimum
flows listed on page 13
9 IOM 1322-1 • WATER-COOLED SCROLL COMPRESSOR
Application Considerations
or page 14.