Daikin Navigator WWV Installation, Operation And Maintenance Manual page 29

Valve Stage Mode
This mode is enabled when the Valve/VFD Control set point
is set to Valve Stage. The valve position should be 0% when
the condenser state is not Run. When the condenser state
becomes Run, the valve position will be controlled to a position
limited to a range from the Valve Minimum Position set point to
the Valve Maximum Position set point.
In this mode the valve position is calculated by a PID loop to
control the condenser EWT or LWT (as selected by the Tower
Control set point) to the active set point. The active set point is
selected based on the fan stage as shown below:
Tower Fan Stage Active Set Point
0 Valve/VFD Set Point
1 Tower Fan Stage 1 On Temperature
2 Tower Fan Stage 2 On Temperature
Cooling Tower Fan VFD
When the Valve/VFD Control set point is set to None, Valve
Setpoint, or Valve Stage, cooling tower fan VFD control should
not be operational and the speed should always be set to 0%.
If the Valve/VFD Control Configuration set point is set to
VFD Stage or Valve SP/VFD Stage then VFD speed will be
controlled as described below.
When active a VFD speed is calculated and limited to a range
defined by the VFD Minimum Speed set point and the VFD
Maximum Speed set point.
The VFD speed should always be 0% when the fan stage is 0.
When one or both fan stages are on, the VFD speed should be
calculated using a PID loop to control the condenser EWT or
LWT (as selected by the Tower Control set point) to the active
set point. The active set point is selected based on the fan
stage as shown below.
Tower Fan Stage Active Set Point
0 N/A
1 Tower Fan Stage 1 On Temperature
2 Tower Fan Stage 2 On Temperature
As the calculated speed varies from 0 to 100%, the voltage
signal for the Tower VFD Speed output should vary from 0 to
10 VDC.
Leaving Water Temp (LWT) Target
The LWT Target varies based on settings and inputs. The base
LWT Target is selected as shown
www.DaikinApplied.com
inTable 28.
Table 28: LWT Targets Control Source
"
Available Control
Modes Set Source
Point Set Point
Local
COOL
Network
Local
Cool w/Glycol
Network
Local
Cool/Ice w/
Glycol
Network
Local
Ice w/Glycol
Network
LWT Reset
The base LWT target may be reset to a higher value if the unit
is in Cool mode and LWT Reset Enable is enabled.
When the reset is active, it will be 0 if the reset signal is less
than or equal to 4 mA. Reset is equal to the Max Reset set
point if the reset signal equals or exceeds 20 mA. The amount
of reset will vary linearly between these extremes if the reset
signal is between 4 mA and 20 mA.
Figure 18: 4-20mA Reset
Base LWT
Target + Max
Reset
Active
LWT
Max Reset
Target
Base LWT
Target
When the active reset increases, the Active LWT Target is
changed at a rate of 0.1 °C (0.18 °F) every 10 seconds. When
the active reset decreases, the Active LWT Target is changed
all at once.
After reset is applied, the LWT target can never exceed a value
of 20.0°C (68°F). Since the Cool LWT set point can be set as
high as 20.0°C, the amount of reset may be limited in order
to meet this requirement to clamp the active LWT target to
20.0°C.
Unit Capacity Control
Unit capacity control will be performed as described in this
section. A combination of starting/stopping circuits and loading/
unloading circuits is used to control the overall unit capacity.
29 IOM 1264-1 • NAVIGATOR
u f
nIT
Mode BAS
Base LWT Target
Input Request
- - Cool Set Point
- - BAS Cool Set Point
- - Cool Set Point
- - BAS Cool Set Point
Off - Cool Set Point
On - Ice Set Point
- Cool BAS Cool Set Point
- Ice BAS Ice Set Point
- - Ice Set Point
- - BAS Ice Set Point
-
4 20 mA Reset
0 4 20
Reset Signal (mA)
MODEL WWV CHILLERS
®
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