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www.DaikinApplied.com 25
IOM 1264-1 • NAVIGATOR
®
MODEL WWV CHILLERS
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Calculations
Evaporator
Error
LWT Error = Evaporator LWT - Active LWT Set Point
Slope
EWT slope is calculated such that the slope represents the
estimated change in EWT over a time frame of one minute.
Unit Enable
Enabling and disabling the chiller is accomplished using set
points and inputs to the chiller. The Unit Switch, Remote Switch
Input, and Unit Enable Set Point all are required to be On/
Enable for the unit to be enabled when the control source is
set to Local. The same is true if the control source is set to
Network, with the additional requirement that the BAS Enable
set point be Enable.
Table 25: Enable Combinations
Unit
Switch
Control
Source
Set Point
Remote
Switch
Input
Unit
Enable
Set Point
BAS
Request
Unit
State
Off
-
-
-
-
Disable
-
-
-
Disable
-
Disable
-
-
Disable
-
-
Disable
On
Local
Enable
Enable
-
Enable
-
Network
-
-
Disable
Disable
On
Network
Enable
Enable
Enable
Enable
All of the methods for disabling the chiller, discussed in this
section, will cause a normal shutdown of any running circuits.
Unit Mode Selection
The operating mode of the unit is determined by set points and
inputs to the chiller. The Available Modes Set Point determines
what modes of operation can be used. This set point also
determines whether the unit is configured for glycol use. The
Control Source Set Point determines where a command to
change modes will come from.
The Available Modes Set Point must only be changed when the
unit switch is off. This is to avoid changing modes of operation
inadvertently while the chiller is running. Unit Mode is set
according to the following table.
Table 26: Unit Mode Combinations
Available Modes
Set Point
Control
Source
Set Point
Mode
Input
BAS
Request
Unit
Mode
Cool
-
-
-
Cool
Cool w/Glycol
-
-
-
Cool
Cool/Ice w/Glycol
Local
Off
Cool
Cool/Ice w/Glyco
Local
On
Ice
Cool/Ice w/Glyco
Network
Cool
Cool
Cool/Ice w/Glyco
Network
Ice
Ice
Ice w/Glycol
-
-
-
Ice
Test
-
-
-
Test
Glycol Configuration
If the Available Modes Set Point is set to a value ‘w/Glycol’,
then glycol limits should be enabled for the unit. This means
that various pressure and temperature settings can be set
to lower values as a result of the glycol limits being enabled.
Once glycol limits are enabled, they should only be disabled
when the Available Modes Set Point is set to Cool.
Unit Control States
The unit will always be in one of three states:
1. Off – Unit is not enabled to run.
2. Auto – Unit is enabled to run.
3. Pumpdown – Unit is doing a normal shutdown.
T1 - Off to Auto
. All of the following are required:
• Unit is enabled
• No unit alarm requiring shutdown is active
• Circuit is available to start
•
Unit configuration is valid
T2 - Auto to Pumpdown
. Any of the following are required:
• Unit is disabled
• Unit alram requiring normal shutdown is active
T3 - Pumpdown to Off
. Any of the following are required:
• Unit alarm requiring rapid shutdown is active
• Circuit is in the Off state
T4 - Auto to Off
. Any of the following are required:
• Unit alram requiring normal shutdown is active
• Circuit disabled and unit in Off state
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