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IOM 1210-1 • MAGNITUDE
®
MODEL WMC CHILLERS
o
peraTIon
Figure 37:
(III) VALVE STAGE -
Valve Opening vs. Temperature
As shown in
Figure 37
, the default minimum and maximum
valve opening positions are 20% 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 first fan.
Up to three more fans are staged on and off and there is
no bypass valve. See
Figure 38
and
Figure 39
.
Figure 38:
TOWER Setpoint - SP2 - (IV) VFD STAGE
Figure 39:
(IV) VFD STAGE - VFD Speed vs. Temperature
As shown in
Figure 39
, 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 40
and
Figure 41
.
Figure 40:
TOWER Setpoint - SP2 - (V) VALVE SP /
VFD STAGE
Figure 41:
(V) VALVE SP / VFD STAGE
Percent vs. Temperature
As shown in
Figure 41
, 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
41
shows that the default temperature at which the valve opens
completely is 65°F. This temperature is the Valve SP and is
adjustable.
0
20
40
60
80
100
65
70
75
80
85
90
Va
lv
e O
pe
ni
ng
(%
)
Temperature (°F)
4 Fan Stages
1 Fan Stage
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
VF
D S
pe
ed
(%
)
Temperature (°F)
4 Fan Stages
1 Fan Stage
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
Pe
rc
en
t (
%
)
Temperature (°F)
% VFD Speed (4 Fan Stages)
% VFD Speed (1 Fan Stage)
% Valve Opening
