IOM 1206-7 • TRAILBLAZER
™
MODEL AGZ CHILLERS
62 www.DaikinApplied.com
U
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UnCTIons
the Control Band:
• Start Up Temperature = Stage Up Tempe Start Up
Delta set point
• Shutdown Temperature = Stage Down Temperature –
Shutdown Delta set point
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’ 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 building automation system
(BAS) Enable set point must be ‘on’. The BAS should enable
the chiller only when there is a demand for cooling.
Unit is enabled according to the following table:
Unit
Switch
Control
Source
Set
Point
Remote
Switch
Input
Unit
Enable
Set
Point
BAS
Enable
Set
Point
Unit
Enable
Off
Off
Off
Off
Off
Off
On
Local
On
On
On
Network
Off
Off
On
Network On
On
On
On
Unit Mode Selection
The operating mode of the unit is determined by setpoints 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. A digital input switches
between cool mode and ice mode if they are available and
the control source is set to ‘local.’ The BAS mode request
switches between cool mode and ice mode if they are both
available and the control source is set to ‘network.’
The Available Modes Set Point should only be changeable
when the unit switch is off. This is to avoid changing modes of
operation inadvertently while the chiller is running.
Table 55: Unit Mode Settings
Control
Source Set
Point
Mode Input BAS
Request
Available
Modes Set
Point
Unit Mode
Cool
Cool
Cool w/
Glycol
Cool
Local
Off
Cool/Ice w/
Glycol
Cool
Local
On
Cool/Ice w/
Glycol
Ice
Network
Cool
Cool/Ice w/
Glycol
Cool
Network
Ice
Cool/Ice w/
Glycol
Ice
Ice w/Glycol Ice
Test
Test
Glycol Configuration
If the Available Modes Set Point is set to an option ‘w/Glycol,’
then glycol operation should be enabled for the unit. Glycol
operation should only be disabled when the Available Modes
Set Point is set to ‘Cool.’
Unit States
The unit will always be in one of three states:
Off – Unit is not enabled to run
Auto – Unit is enabled to run
Pumpdown – Unit is doing a normal shutdown (tube and fin
condenser coils only). If a unit has microchannel coils, the
individual refrigerant circuits will never do a pumpdown. So
if the conditions for the Auto to Pumpdown transition occur,
the unit state will transition from Auto to Pumpdown and
then immediately to Off.
Transitions between these states are shown in the following
diagram.
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