Johnson Controls System 450 Series Technical Bulletin

Supported alarms
Table 15: System settings
Description Alarm
Display
indicator
Notes
Temperature Sensor
Sn-1
High Temperature S1-H Auto resets when Sn-1 drops to
80% of the high temperature alarm
set-point. This alarm is disabled
during defrost. There is a user-
defined alarm delay for the high
temperature alarm. This delay
displays in units of minutes.
Temperature
Sensors Sn-1 and
Sn-2 & Pressure
Transducer Sn-3
Sensor failure, Open or
shorted Condition
SNF Auto resets when the alarm
condition no longer exists. There is
a fixed thirty second delay for the
sensor failure alarm.
System 450
communications
bus
Communication failure
between System 450
control and expansion
modules
bUS The bUS ALRM screen shows
the sequential number of the
Expansion Module which is
not in communication with the
Control Module. Auto resets when
communications are re-established.
The alarm activates after three
consecutive communication faliures.
Defrost termination Defrost termination
failure
dtEr FAIL Occurs when an active defrost,
with a defined termination sensor,
runs the full defrost cycle without
reaching the termination setting
defined value. Auto resets when
the next defrost cycle starts, either
manually or scheduled. The alarm
displays again if the next defrost
terminates on time and not on
temperature.
Defrost error Defrost termination
sensor reading is at
or above termination
setting at the start of
the defrost cycle
dErr NOTC Auto resets if the termination sensor
does not indicate a termination
condition when the next active
defrost starts. You can start a
manual defrost to clear the alarm
manually. The alarm displays again
if the termination sensor is at or
above the defrost termination
setting at the start of the next
defrost cycle.
33System 450 Series C450CCU Condensing Unit Control System Technical Bulletin

Johnson Controls System 450 Series Specifications

General

Brand	Johnson Controls
Model	System 450 Series
Category	Control Unit
Language	English