Daikin Magnitude WME Series - Page 38

IOM 1266-2 • MAGNITUDE
®
MODEL WME CHILLERS 38 www.DaikinApplied.com
operaTIon
Tower Control Settings
There are ve 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 Figure
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
efciency. Using the MicroTech
®
controller, up to two Digital
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 Figure 44 on page
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 dene the lift pressure between the Evaporator
Pressure and the Condenser Pressure.
Setpoint for Tower Valve / Fan VFD Strategy on the TOWER
Setpoint Screen denes if and how the two MicroTech
®
Analog
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 ve
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): In this mode, a
VFD controls the rst fan. An additional fan is staged on and off
and there is no bypass valve. See Figure 45 and Figure 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 VFD STAGE for control of the VFD speed
based on temperature or lift.
Figure 45: Strategy (I) - VFD STAGE
Figure 46: Strategy (I) VFD STAGE - VFD Speed vs. Temp
As shown in Figure 46, 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.
Strategy (II) VALVE SP: This control strategy is
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 Figure 47 and Figure 48.
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 ow
through the tower until the last fan is staged off. Other
settings when TEMP is selected:
Condenser
0-10 VDC
Signal
Cooling Tower
Fan Staging
(Up to 2 fans)
MicroTech
®
Controller
Tower
Control
Panel
w/ Fan
VFD
0
20
40
60
80
100
65 70 75 80 85 90
VFD Speed (%)
Temperature (°F)
2 Fan Stages 1 Fan Stage