IOM 1210-7 • MAGNITUDE
®
MODEL WMC CHILLERS 42 www.DaikinApplied.com
operaTIon
to smooth the control and reduce fan cycling. See Figure
38 and Figure 41.
Figure 40: TOWER Setpoint - SP2 - (III) VALVE STAGE
Figure 41: (III) VALVE STAGE -
Valve Opening vs. Temperature
As shown in Figure 41, the default minimum and maximum
valve opening positions are 10% and 100%, respectively.
These minimum and maximum positions are adjustable
anywhere between 0% and 100%. Additional fans stage on
when the valve opening position reaches the maximum value
that was set.
(IV) VFD STAGE: In this mode, a VFD controls the rst fan.
Up to three more fans are staged on and off and there is
no bypass valve. See Figure 42 and Figure 43.
Figure 42: TOWER Setpoint - SP2 - (IV) VFD STAGE
Figure 43: (IV) VFD STAGE - VFD Speed vs. Temperature
As shown in Figure 43, 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.
(V) VALVE SP / VFD STAGE: This control strategy is tower
fan control with a VFD and bypass valve control. See
Figure 44 and Figure 45.
Figure 44: TOWER Setpoint - SP2 - (V) VALVE SP /
VFD STAGE
Figure 45: (V) VALVE SP / VFD STAGE -
Percent vs. Temperature
Condenser
Bypass Line
0-10 VDC Signal
Bypass
Valve
Cooling Tower
Fan Staging
(Up to 4 fans)
MicroTech
®
II
Controller
Tower
Control
Panel
0
20
40
60
80
100
65 70 75 80 85 90
Condenser
0-10 VDC
Signal
Cooling Tower
Fan Staging
(Up to 4 fans)
MicroTech
®
II
Controller
Tower
Control
Panel
w/ Fan
VFD
0
20
40
60
80
100
65 70 75 80 85 90
Condenser
MicroTech
®
II
Controller
0-10 VDC
Signal
Bypass Line
0-10 VDC Signal
Bypass
Valve
Cooling Tower
Fan Staging
(Up to 4 fans)
Tower
Control
Panel
w/ Fan
VFD
0
20
40
60
80
100
60 65 70 75 80 85 90
% VFD Speed (4 Fan Stages)
% VFD Speed (1 Fan Stage)
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