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Tower Control Settings
There are five possible tower control strategies: (I) VFD
STAGE, (II) VALVE SP, (III) VALVE STAGE, (IV) NONE,
and (V) VALVE SP/VFD STAGE. These control strategies
are selected from the TOWER Setpoint Screen (see
44 on page
36) using the Tower Valve/Fan VFD Strategy
setting. (In this section for Tower Control Settings, "SP" means
"Setpoint.") An explanation of each control strategy follows this
paragraph. Along with each explanation is a diagram and graph
to help illustrate the control strategy. Note that these graphs
illustrate the default conditions for each strategy.
Setting Tower Control Using the HMI Panel
MicroTech
may assist in the head control either directly
®
or through inputs to a BAS to optimize performance and
efficiency. Using the MicroTech
Outputs of Tower Staging along with two Analog Outputs (0-10
VDC) are available. The two Analog Outputs are as follows:
1. Bypass Valve signal
2. Tower Fan VFD signal
Setup for any tower control will be accomplished on the HMI
using the TOWER Setpoint Screen (see
36
and
Table 16 on page
37).
Setpoint for Cooling Tower Control on the TOWER Setpoint
Screen sets the type of control. NONE is selected as default.
Choose TEMPERATURE for entering condenser water control
or LIFT to define the lift pressure between the Evaporator
Pressure and the Condenser Pressure.
Setpoint for Tower Valve / Fan VFD Strategy on the TOWER
Setpoint Screen defines if and how the two MicroTech
Outputs (Bypass Valve signal and Tower Fan VFD signal)
will be used with the Staging selected for the tower. A BAS or
other control may monitor these outputs to understand when or
how much the MicroTech
would recommend for proper head
®
control on the WME unit. Setup instructions for each of the five
tower control strategies are provided next.
Cooling Tower Stages on the TOWER Setpoint Screen sets the
number of tower stages.
Strategy (I) VFD STAGE (Default):
VFD controls the first fan. An additional fan is staged on and off
and there is no bypass valve. See
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 VFD STAGE for control of the VFD speed
based on temperature or lift.
IOM 1266-2 • MAGNITUDE
Figure
controller, up to two Digital
®
Figure 44 on page
®
In this mode, a
Figure 45
and
Figure
MODEL WME CHILLERS
®
Figure 45: Strategy (I) - VFD STAGE
Cooling Tower
Fan Staging
(Up to 2 fans)
0-10 VDC
Signal
MicroTech
®
Controller
Condenser
Figure 46: Strategy (I) VFD STAGE - VFD Speed vs. Temp
100
80
60
40
20
0
65
Analog
As shown in
Figure
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.
Strategy (II) VALVE SP
tower staging (up to two stages) with a low-limit controlled
bypass valve. The tower fans are controlled as in method (I),
plus a tower bypass valve is controlled to provide a minimum
condenser EWT. There is no interconnection between the fan
control and the valve control. See
46.
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 for control of the bypass valve
based on temperature or lift.
Tower Valve Type. Select NC or NO depending if valve
is normally closed to the tower with no control power or
normally open to the tower with no control power.
B. If TEMP was selected for Cooling Tower Control, set the
Valve Target Temperature, default is 65°F. This setpoint
is usually 5°F below the minimum fan stage setpoint
established with Stage #1 setting. This keeps full flow
through the tower until the last fan is staged off. Other
settings when TEMP is selected:
38
Tower
Control
Panel
w/ Fan
VFD
70
75
80
Temperature (°F)
2 Fan Stages
1 Fan Stage
46, the default minimum and maximum
:
This control strategy is
Figure 47
and
www.DaikinApplied.com
o
peraTIon
85
90
Figure
48.
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