Daikin Magnitude - Page 45

www.DaikinApplied.com 43 IOM 1210-7 • MAGNITUDE
®
MODEL WMC CHILLERS
operaTIon
As shown in Figure 45, 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
45 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
®
II
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
®
II controller. See Figure 46.
Figure 46: BAS Alternate
Setting Tower Control Using the HMI Panel
MicroTech
®
II may assist in the head control either directly
or through inputs to a BAS to optimize performance and
efciency. Using the MicroTech
®
II, up to four Digital Outputs of
Tower Staging along with three Analog Outputs (0-10 VDC) are
available. The three Analog Outputs are as follows:
1. Bypass Valve signal
2. Tower Fan VFD signal
3. Tower Reset signal: Dened by a voltage to offset the
tower control setting. If the MicroTech
®
II is controlling
the tower, this signal is not used.
Setup for any tower control will be accomplished on the HMI
using the TOWER Setpoint Screen (see Figure 35 on page
40) and the VALVE Setpoint Screen (see Figure 34 on page
39).
Setpoint 1 (Cooling Tower Control) on the TOWER Setpoint
Screen sets the type of control. NONE is selected as default.
Choose TEMP for entering condenser water control or LIFT to
dene the lift pressure between the Suction pressure and the
Discharge pressure.
Setpoint 3 (Cooling Tower Stages) on the TOWER Setpoint
Screen sets the number of tower stages that the tower has.
Setpoint 2 (Tower Bypass Valve / Fan VFD) on the TOWER
Setpoint Screen denes if and how the rst two MicroTech
®
II 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
®
II would recommend for
proper head control on the WMC unit. The third Analog Output
(Tower Reset) is only congurable from the MicroTech
®
II
controller. Commissioning setup of this 0-10 VDC signal, that
will represent the MicroTech
®
II recommending increased
head pressure by a reset voltage, is typically done by the
Daikin Applied startup technician. Setup instructions for each of
the ve tower control strategies are provided next.
(I) NONE: Tower Fan Staging Only (This is the default
setting but it is NOT a recommended control strategy.)
The following settings are used for the Tower Fan Staging Only
mode, (SP = setpoint)
A. TOWER Setpoint Screen
1. SP1. Select TEMP if control is based on condenser
EWT or LIFT if based on compressor lift expressed in
pressure.
2. SP2. Select NONE for no bypass valve or fan VFD
control.
3. SP3. Select one to four fan outputs depending on the
number of fan stages to be used. More than one fan
can be used per stage through the use of relays.
4. SP4. Select FAN STAGE UP TIME from 1 to 60
minutes. The default value of 2 minutes is probably
a good starting point. The value may need to be
adjusted later depending on actual system operation.
5. SP5. Select FAN STAGE DOWN TIME from 1 to 60
minutes. The default value of 5 minutes is probably
a good starting point. The value may need to be
adjusted later depending on actual system operation.
6. If TEMP is selected in SP1, use
a. SP6. Select STAGE DIFFERENTIAL in degrees F.
Start with default of 3°F.
b. SP8-11. Set the STAGE ON temperatures
consistent with the temperature range over which
the condenser EWT is desired to operate. The
default values of 70°F, 75°F, 80°F and 85°F are a
good place to start in climates with moderate wet
bulb temperatures. The number of STAGE ON
setpoints used must be the same as SP3.
7. If LIFT is selected in SP1, use
a. SP7. Select STAGE DIFFERENTIAL in PSI. Start
with default of 6.0 PSI.
b. SP12-15. Start with default setpoints. The number
of STAGE ON setpoints used must be the same as
SP3.
(II) VALVE SP: Tower Fan Staging With Bypass Valve
Controlling Minimum EWT
A. TOWER Setpoint Screen
1. Use all of the same setpoint settings as those outlined
in section I.A [the TOWER Setpoint Screen section for
control strategy (I) NONE] except for SP2. For SP2,
select VALVE SP for control of the bypass valve based
on temperature or lift.
Condenser
MicroTech
®
II
Controller
Bypass Line
0-10 VDC Signal
BAS
Tower
Control
Panel
w/ Fan
VFD