operaTIon
www.DaikinApplied.com 41 IOM 1266-2 • MAGNITUDE
®
MODEL WME CHILLERS
Strategy (V) VALVE SP/VFD STAGE: This control
strategy is tower fan control with a VFD and bypass valve
control. See Figure 53 and Figure 54.
To set up in HMI:
A. The TOWER Setpoint setting for Cooling Tower Control
strategy should be NONE. Tower Valve/VFD should be
changed to VALVE SP/VFD STAGE.
B. Use all of the same setpoint settings as outlined in
Strategy (II) - section B for Temp or section C for Lift.
Figure 53: Strategy (V) - VALVE SP/VFD STAGE
Figure 54: Strategy (V) VALVE SP/VFD STAGE -
Percent vs. Temperature
As shown in Figure 54, the default minimum and maximum
VFD speeds are 20% and 100%, respectively. These minimum
and maximum values are adjustable anywhere between 0%
and 100%. Additional fans stage on when the VFD speed
reaches the maximum value that was set. In addition, Figure
54 shows that the default temperature at which the valve opens
completely is 65°F. This temperature is the Valve SP (also
called Valve Target) and is adjustable.
BAS Alternate
In control strategies (I) through (V), the chiller MicroTech
®
is directly controlling the cooling tower fan staging, variable
frequency drives, and bypass valves. As an alternative, a BAS
can control these components based on a signal from the
MicroTech
®
controller. See Figure 55.
Figure 55: BAS Alternate
Condenser
MicroTech
®
Controller
0-10 VDC
Signal
Bypass Line
0-10 VDC Signal
Bypass
Valve
Cooling Tower
Fan Staging
(Up to 2 fans)
Tower
Control
Panel
w/ Fan
VFD
0
20
40
60
80
100
60 65 70 75 80 85 90
Percent (%)
Temperature (°F)
% VFD Speed (2 Fan Stages) % VFD Speed (1 Fan Stage)
% Valve Opening
Condenser
MicroTech
®
Controller
Bypass Line
0-10 VDC Signal
BAS
Tower
Control
Panel
w/ Fan
VFD
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