Page 23 of 29 Revision 3.3 Feb 2021
ProReact EN Analogue Installation Manual
Document Ref. PACC-MAN
Alarm Conditions
24. If the current measured resistance of the sensor cable (“Curr”) drops
below the alarm threshold (as shown on the display right), the control
unit will trigger an alarm. (Note: the pre-alarm threshold is not shown on
the built-in display. The laptop/PC software must be used to determine
this value). The alarm output will be set and the alarm LED will illuminate
25. If the rate-of-change of the resistance of the cable exceeds a preset
value (equal to when approximately 2% of the cable is heated at greater
than 15°C/min for at least 3 minutes), a rate alarm may be triggered. The
alarm output will be set, the alarm LED will illuminate and the display will
show “Rate Alarm”.
26. If the measured average ambient temperature of whole sensor cable
exceeds the alarm temperature for the chosen alarm setting, the control
unit will trigger an alarm. For example, in this case the measured ambient
temperature is 63.4°C which is above the alarm temperature for the
whole cable on alarm setting Class A1I/A2I. The alarm output will be set
and the alarm LED will illuminate.
CU R R: 2 5M Ω
1 3.4
O
C A: 45MΩ
CURR: 100MΩ
6 3.4
O
C A: 45MΩ
CU R R: 4 5 MΩ
1 3.4
O
C RATE ALARM
LED Illustrations
Alarm Fault Power
Pre
Alarm
Alarm Fault Power
Pre
Alarm
Alarm Fault Power
Alarm Fault Power
Pre
Alarm
Alarm Fault Power
Pre
Alarm
Alarm Fault Power
Alarm Fault Power
Pre
Alarm
Alarm Fault Power
Pre
Alarm
Alarm Fault Power
Resetting the control unit after an alarm condition
Following an alarm condition the alarm (or pre-alarm) output will
latch (remain set) until the control unit is reset. Providing none of the
conditions listed in steps 24-26 remain, there are several methods to reset
the alarm condition:
1. Press the SET button on the control unit for >3s to clear the alarm
condition.
2. Provide 5-28Vdc to the Remote Reset input for >3s (see “Control
Module Wiring”).
3. Send a “Write Single Coil (0x05)” command to coil address 0 via the
Modbus RS-485 connection.
4. Interrupt power to the control unit for at least 3s.
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