Operation
www.DaikinApplied.com 53
IOM 1281-2 • CENTRIFUGAL WATER CHILLERS
Figure 59: Strategy (IV) - NONE
Figure 60: Strategy (IV) NONE - Temp vs. Fan Stages
Strategy (V) VALVE SP /VFD STAGE:
This control strategy is tower fan control with a VFD and
bypass valve control. See
Figure 61
and
Figure 62
.
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 61: Strategy (V) - VALVE SP/VFD STAGE
Figure 62: Strategy (V) VALVE SP / VFD STAGE -
Percent vs. Temperature
As shown in
Figure 62
, 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
62
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 63
.
Figure 63: BAS Alternate
Condenser
Cooling Tower
Fan Staging
(Up to 3 fans)
Tower
Control
Panel
MicroTech
®
Controller
65
70
75
80
85
90
95
0
1
2
3
4
5
Te
m
pe
ra
tur
e (
°F)
Fan Stages
Condenser
MicroTech
®
Controller
0-10 VDC
Signal
Bypass Line
0-10 VDC Signal
Bypass
Valve
Cooling Tower
Fan Staging
(Up to 3 fans)
Tower
Control
Panel
w/ Fan
VFD
0
20
40
60
80
100
60
65
70
75
80
85
90
Pe
rc
en
t (
%
)
Temperature (°F)
% VFD Speed (3 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
