Rockwell Automation 900-TC32 Digital Temperature Controllers, Series B - Manual (Page 184)

Publication 900-UM007D-EN-E - January 2011
4-48 Parameter Adjustments & Application Considerations
If the control deviation is reduced in the area between 5 and 6 (i.e., the set
point is approached) and the amount the control deviation is reduced is at least
equal to the LBA Band, the Loop Break Alarm will turn OFF.
If the control deviation is reduced in the area between 6 and 7 (i.e., the set
point is approached) and the amount the control deviation is reduced is less
than the LBA Band, the Loop Break Alarm will turn ON.
• If the LBA Detection Time, LBA Level, LBA Detection Band, and PID
settings are not appropriate, alarms may be detected inappropriately or
alarms may not be output when necessary.
• Loop break alarms may be detected if unexpectedly large process
disturbances occur continuously and a large deviation does not decrease.
• If a loop break occurs when the set point is near the ambient
temperature, the temperature deviation in a steady state may be less than
the LBA level, preventing detection of the loop break.
• If the set point is so high or low that it cannot be reached even with a
saturated manipulated variable, a temperature deviation may remain
even in a steady state and a loop break may be detected.
• Loop Break Detection in not possible if a fault occurs that causes an
increase in temperature while control is being applied to increase the
temperature (e.g., an SSR short-circuit fault).
• Loop Break Detection in not possible if a fault occurs that causes a
decrease in temperature while control is being applied to decrease the
temperature (e.g., a heater burnout fault).