User`s guide

Series D8 User’s Guide Chapter 7: Troubleshooting and Reconfiguring
Doc. 0600-3120-2000 Watlow Anafaze 159
Process Alarms
When a process alarm occurs, the controller switches to the
single-loop display for the loop with the alarm and displays
the alarm code (see Alarm Displays on page 81).
Possible Causes of a Process Alarm
In a heating application, a low alarm or low deviation alarm
may indicate one of the following:
• The heater has not had time to raise the temperature.
• The load has increased and the temperature has fallen.
• The control mode is set to manual instead of automatic.
• The heaters are not working because of a hardware fail-
ure.
• The sensor is not placed correctly and is not measuring
the load’s temperature.
• The alarm settings are too tight. The process variable var-
ies by more than the alarm limits because of load chang-
es, lag or other system conditions.
• The system is so poorly tuned that the temperature is cy-
cling about set point by more than the alarm set point.
NOTE! In cooling applications, similar issues cause
high alarms.
In a heating application, a high alarm or high deviation alarm
may indicate one of the following:
• The process set point and high alarm set point have been
lowered and the system has not had time to cool to within
the new alarm setting.
• The controller is in manual mode and the heat output is
greater than 0 percent.
• The load has decreased such that the temperature has ris-
en.
• The heater is full-on because of a hardware failure.
• The system is so poorly tuned that the temperature is cy-
cling about set point by more than the alarm set point.
NOTE! In cooling applications, similar issues cause
low alarms.