SuperNova PD500 PID Process & Temperature Controllers
Instruction Manual
42
Figure 32. Loop Break Alarm (LBA) Operation in
Reverse Action Mode
Direct Action LBA Operation
When the control output value is 100% in the direct
action mode (cooling control), the LBA output turns on
when the temperature does not fall at least the LB.SV
value within the LB.TM set time. Also, when the
control output value is 0%, the LBA output turns on
when the temperature does not rise at least the
LB.SV value within the LB.TM set time.
Heating & Cooling Control LBA
Operation
When OUT1 and OUT2 are both configured for
control outputs, the controller automatically enters
heating and cooling mode. In heating and cooling
mode, the controller is automatically set to reverse
acting. However, the LBA operates as follows.
When the control output value is 100% on the heating
output (H), the LBA alarm output turns on when the
temperature does not rise at least the LB.SV value
within the LB.TM set time.
When the control output value is 100% on the cooling
output (C), the LBA alarm output turns on when the
temperature does not rise at least the LB.SV value
within the LB.TM set time.
LBA Alarm Clear
The LBA is automatically released under the following
conditions.
•
When the difference between the set value
(SV) and process variable (PV) is less than
or equal to the Loop Break Alarm Deadband
(LB.DB) value.
•
When there is no sub relay output assigned
to the LBA.
•
When the controller is set to the STOP state.
•
When performing an auto-tune.
Loop Break Detection Time (LB.TM)
The loop break detection time is usually set to about
twice the value of PID coefficient 1. When auto-
tuning is executed, the LB.TM value is automatically
set to twice the PID coefficient 1 value.
However, when on/off control is used, LB.TM is not
set automatically, so it must be input manually by the
user.
Loop Break Set Value (LB.SV)
When the control output reaches 100% or 0%, an
alarm is generated if the change of the temperature
deviation after LB.TM time does not change by more
than the Loop Break Alarm Set Value (LB.SV).
Loop Break Alarm Deadband
(LB.DB)
To prevent malfunctions of the loop break alarm
during normal control, set the Loop Break Alarm
Deadband (LB.DB). If the PV enters the range of SV ±
LB.DB, the LBA will not turn on, or turn off if already
on.
The LBA will only work if the PV is less than SV-
LB.DB or if PV is greater than SV + LB.DB.
Loop Break Alarm Latch Status
(LB.LS)
LB.LS is the loop break alarm latch reset function.
This parameter is accessible if the Sub Relay Group
(G.SUB) parameter LB.LT is set to ON.
If the Sub Relay Group (G.SUB) parameter LB.LT is
set to OFF, this parameter does not appear in the
menu. The alarm will automatically reset when the
alarm condition is cleared (including deadband).
Releasing a Loop break Alarm in
Latch State
To release a loop break alarm with the latch status
ON, the operator must change this parameter to RST
after the loop break alarm condition has cleared.
As a shortcut, the operator may press the DOWN or
UP arrow keys to reset a latched alarm after the alarm
condition has cleared.