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www.DaikinApplied.com 65
IOM 1206-7 • TRAILBLAZER
™
MODEL AGZ CHILLERS
Freeze Protection
To protect the evaporator from freezing, the evaporator pump
will start if all of the following are true:
• LWT equal to or less than the Evap Freeze set point for at
least three seconds
• LWT sensor fault isn’t active
•
manual reset flow loss alarm is not active
Freeze protection will end when any of the following are true:
• [LWT is at least 1.11°C (2°F) above the Evap Freeze set
point OR LWT sensor fault is active] and pump has been
in run state for at least 15 minutes
•
manual reset flow loss alarm is active
Pump Selection
The pump output used will be determined by the Evap
Pump Control set point. This setting allows the following
configurations:
• #1 only – Pump 1 will always be used
• #2 only – Pump 2 will always be used
• Auto – The primary pump is the one with the least run
hours, the other is used as a backup
• #1 Primary – Pump 1 is used normally, with pump 2 as a
ackup
• #2 Primary – Pump 2 is used normally, with pump 1 as a
backup
Primary/Standby Pump Staging
The pump designated as primary will start first. If the
evaporator state is start for a time greater than the recirculate
timeout set point and there is no flow, then the primary pump
will shut off and the standby pump will start. When the
evaporator is in the run state, if flow is lost for more than half
of the flow proof set point value, the primary pump will shut
off and the standby pump will start. Once the standby pump
is started, the flow loss alarm logic will apply if flow cannot be
established in the evaporator start state, or if flow is lost in the
evaporator run state.
Auto Control
If auto pump control is selected, the primary/standby logic
above is still used. When the evaporator is not in the run state,
the run hours of the pumps will be compared. The pump with
the least hours will be designated as the primary at this time.
LWT Target
The LWT Target varies based on settings and inputs.
The base LWT Target is selected as follows:
Control
Source Set
Point
Mode Input BAS
Request
Available
Modes Set
Point
Base LWT
Target
Local
OFF
-
COOL
Cool Set
Point 1
Local
ON
-
COOL
Cool Set
Point 2
Network
-
-
COOL
BAS Cool
Set Point
Local
OFF
-
COOL w/
Glycol
Cool Set
Point 1
Local
ON
-
COOL w/
Glycol
Cool Set
Point 2
Network
-
COOL w/
Glycol
BAS Cool
Set Point
Local
OFF
-
COOL/ICE
w/Glycol
Cool Set
Point 1
Local
ON
-
COOL/ICE
w/Glycol
Ice Set
Point
Network
-
COOL
COOL/ICE
w/Glycol
BAS Cool
Set Point
Network
-
ICE
COOL/ICE
w/Glycol
BAS Ice Set
Point
Local
-
-
ICE w/
Glycol
Ice Set
Point
Network
-
-
ICE w/
Glycol
BAS Ice Set
Point
Leaving Water Temperature (LWT) Reset
The base LWT target may be reset if the unit is in Cool mode
and LWT reset is enabled via the set point.
The reset amount is adjusted based on the 4 to 20 mA reset
input. Reset is 0° if the reset signal is less than or equal to
4 mA. Reset is 5.56°C (10.0°F) 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.
When the reset amount increases, the Active LWT Target is
changed at a rate of 0.1°C every 10 seconds. When the active
reset decreases, the Active LWT Target is changed all at once.
After the reset is applied, the LWT target can never exceed a
value of 18.33°C (65°F).
Summary of Contents for AGZ030E
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