Alarms and Events
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IOM 1242-8 • PATHFINDER
®
MODEL AWV CHILLERS
High Condenser Pressure
Alarm:
High Condenser Pressure
Displayed Text: Cn CondPressHigh
Trigger:
Saturated Condenser Temp > Max
Saturated Condenser Value for time longer
than High Condenser Pressure Delay set
point.
Action Taken:
Rapid shutdown of circuit and lock out from
running
Reset:
This alarm can be cleared manually via
the Unit Controller keypad if Saturated
Condenser Temp < Max Saturated
Condenser Value.
Low Pressure Difference Or Ratio
Alarm:
Low Pressure Difference Or Ratio
Displayed Text:
Cn LowPrDiffOrRatio
Trigger:
This alarm is triggered on the third
occurrence of the below conditions within
two hours. Prior occurrences are events.
Trigger 1:
Pressure ratio is < 1.6 for longer than the
Low Pressure Diff/Ratio Delay set point after
circuit state transition to Run. Pressure ratio
is calculated as shown with pressures in
kPa:
Ratio = (Cond Press + 101.325)/(Evap
Press + 101.325)
Trigger 2:
Pressure difference is less than 180 kPa for
longer than the Low Press Diff/Ratio Delay
set point after circuit state transition to Run.
Press difference is calculated as shown in
kPa:
Difference = (Cond Pressure) - (Evap
Pressure)
Alarm/event cannot trigger for 5 minutes
after circuit state transitions to Preopen if
OAT < 7°C, however the trigger logic will still
run during this window.
Action Taken:
Rapid shutdown of circuit and lock out from
running
Reset:
This alarm should auto reset every time
until it has triggered 3 times within 2 hours
and be cleared manually via Unit Controller
keypad or BAS.
Mechanical Low Pressure Switch
Alarm:
Mechanical Low Pressure Switch
Displayed Text: Cn MLP Switch
Trigger:
The alarm is triggered if all of the following
are true for at least 40 seconds:
• Circuit State is Run
• MLP Switch input is off
The alarm also requires Evaporator
Configuration = Remote to trigger. This
means if the Evaporator Configuration is set
to Packaged then the MLP Switch inputs are
ignored and the alarm is disabled..
Action Taken:
Rapid shutdown of circuit and lock out from
running.
Reset:
This alarm can be cleared manually via the
controller HMI if the MLP Switch input is on.
Mechanical High Pressure Switch
Alarm:
Mechanical High Pressure Switch
Displayed Text: Cn MHP Switch
Trigger:
With F3 and F4 compressor types:
Compressor VFD reports Safe Disable Input
alarm. This is the case when the alarm code
reported by the VFD is either 003B or 003C
(hex).
With 3120 and 3122 compressor types:
This alarm will trigger if the compressor VFD
reports the Safe Torque Off alarm. This is
detected when register 8196 (Active Alarm
Group word) bit 13 is set and register 532
(Alarm Code 13) = 1, both for two seconds.
Action Taken:
Rapid shutdown of circuit and lock out
from running. Note that VFD will shut down
compressor directly in response to this
alarm in the VFD. Controller then needs to
move circuit to the off state, but compressor
should already be turned off by the VFD.
Reset:
With F3 and F4 compressor types:
This alarm can be cleared manually via
the controller HMI if the VFD is no longer
reporting the Safe Disable Input alarm for at
least a minute.
With 3120 and 3122 compressor types:
This alarm can be cleared manually via the
controller HMI. When the alarms are cleared
in the controller, the command to clear
alarms in the VFD’s should be sent to them.
