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36.0% to 36.0 % of PB1 (or PB2 if PB2 is selected). A negative DB value shows an overlap area over which
both outputs are active. A positive DB value shows a dead band area over which neither output is active
5.2.4.4 Heater Break Alarm
A current transformer CT94-1 should be installed to detect the heater current if a heater break
alarm is required. The CT signal is sent to input 2, and the PV2 will indicate the heater current in 0.1 Amp.
Resolution. The range of current transformer is 0 to 50.0 Amps.
Example
A furnace uses two 2KW heaters connected in parallel to warm up the process. The line voltage
is 220V and the rating current for each heater is 9.09A. If we want to detect any one heater break, set
A1SP=13.0A, A1HY=0.1 A1FN=PV2.L, A1MD=NORM, then
5.2.4.5 Loop Break Alarm
A1FN selects LB if alarm 1 is required to act as a loop break alarm. Similarly, if alarm 2 is
required to act as a loop break alarm, then set OUT2 with=AL2 and A1FN with LB. TIME, A1SP, A1DV and
A1HY are hidden if alarm 1 is configured as a loop break alarm. Similarly, TIME, A2SP, A2DV and A2HY
are hidden if alarm 2 is configured as a loop break alarm.
One of 4 kinds of alarm modes can be selected for alarm 1 and alarm 2. These are: Normal
alarm, latching alarm, Holding alarm and Latching/Holding alarm. However, the Holding mode and
latching/Holding mode are not recommended to be chosen for loop break alarm since loop break alarm will
not perform holding function even if it is set with holding or latching/holding mode.
Loop Break Conditions are detected during a time interval of 2TI1 (double of integral time, but
120 seconds maximum). Hence the loop break alarm doesn't respond quickly as it occurs. If the process
value doesn't increase (or decrease) while the control variable MV1 has reached to its maximum (or
minimum) value within the detecting time interval, a loop break alarm (if configured) will be actuated.
Loop Break Alarm (if configured) occurs when any of the following condition happens
1 Input sensor is disconnected (or broken).
2 Input sensor is shorted.
3 Input sensor is defective.
4 Input sensor is installed outside (isolated from) the process.
5 Controller fails (A-D converter damaged).
6 Heater ( or generally, chillers, valve, pump, motor etc. ) breaks or fails or uninstalled
7 Switching device (used to drive heater) is open or shorted.
5.2.4.6 Sensor Break Alarm
Alarm 1 or alarm 2 can be configured as sensor break alarm by selecting SENB for A1FN or
A2FN.The sensor break alarm is activated as soon as failure mode occurs. Note that A-D failure also
creates a sensor break alarm. TIME, A1SP, A1DV, and A1HY are hidden if alarm 1 is configured as a
sensor break alarm. Similarly, TIME, A2SP, A2DV and A2HY are hidden if alarm 2 is configured as a sensor
break alarm.
One of 4 kinds of alarm modes can be selected for sensor break alarm. These are: Normal
alarm, latching alarm, Holding alarm and Latching/Holding alarm. However, the Holding alarm and
Latching/Holding alarm are not recommended to be chosen for sensor break alarm since sensor break
alarm will not perform holding function even if it is set with holding or latching/holding mode.
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