Daikin WMC Installation, Operation And Maintenance Manual page 42

Leaving Water Temperature (LWT) Reset
The Active Leaving Water variable shall be set to the current
Leaving Water Temperature (LWT) setpoint unless modified
by one of the reset methods below. (The current LWT setpoint
is Cool LWT as determined by the chiller mode.) The type of
reset in effect is determined by the LWT Reset Type setpoint
(Setpoint 7 of the WATER Setpoint Screen).
Reset Type – NONE
The Active Leaving Water variable is set equal to the current
LWT setpoint.
Reset Type – RETURN
The Active Leaving Water variable is adjusted by the return
water temperature.
When the chiller mode = COOL, the Active Leaving Water
variable is reset using the following parameters:
1. Cool LWT setpoint
2. Max Reset Delta T setpoint
3. Start Reset Delta T setpoint
Reset is accomplished by changing the Active Leaving Water
variable from the (Cool LWT setpoint) to the (Cool LWT
setpoint + Max Reset Delta T setpoint) when the evaporator
(return – leaving) water temperature delta varies from the (Start
Reset Delta T setpoint) to 0.
Reset Type – 4-20mA
The Active Leaving Water variable is set equal to the Cool LWT
setpoint if the reset signal is less than or equal to 4 mA. It is set
equal to (Cool LWT setpoint + Max Reset Delta T setpoint) if
the reset signal equals or exceeds 20 mA. The Active Leaving
Water variable will vary linearly between these extremes if the
reset signal is between 4 mA and 20 mA. An example of this
action is shown in Figure 46.
Figure 46: LWT Reset (Cool Mode)
(54.0°F)
Max Reset Delta T
(10.0°F)
Cool LWT Set-Point
(44.0°F)
0 ma
NOTE: Temperatures in Figure 46
IOM 1210-1 • MAGNITUDE
20 ma
4 ma
are examples only.
MODEL WMC CHILLERS
®
Service Screen
The Service Screen (Figure
the SET button from any SET screen. In other words, it is
the second "SET" screen. While containing information and
activity buttons for the service technician, it also has valuable
information for the operator.
Figure 47: Service Screen
The upper left corner of the Service Screen contains
compressor information such as operating hours and number
of starts for each compressor. "Spare Capacity" is used to set
the compressor stopping increments.
The Active pLAN Nodes matrix (middle left of the screen)
shows active control components on the pLAN. A, B, C, and
D are individual chillers. 1 and 2 are not used on C vintage
chillers, 5 is the unit controller, and 7 is the OITS panel.
The pLAN Comm button and the LOAD UCM button (lower left
of the screen) are used for setting up multiple chillers at startup
by a Daikin Applied startup technician.
Pressing the Date/Time button on the right side of the Service
Screen opens the Date and Time Properties Window, shown
in Figure 48. Change the date and time on the "Date & Time"
tab. To change the date, use the drop down menu to choose
the correct month, use the up and down arrows to scroll to the
correct year, and then select the correct day on the calendar
shown. To change the time, highlight the time in the text field
below the analog clock and use the up and down arrows to
scroll to the correct time. Use the drop down menu in the "Time
Zone" tab to change the time zone to the correct area.
NOTE: It is likely that the chiller will contain the factory
settings for date, time, and time zone; therefore, it is
important to verify or change these settings when the
chiller is first used on the job-site. Failure to do so will
result in incorrectly labeled History files.
40
o
peraTIon
47) is accessed by pressing
www.DaikinApplied.com