Watlow CPC400 - Manual (Page 155)

CPC400 Series User’s Guide Chapter 6: Troubleshooting and Reconfiguring
Doc. 0600-2900-2000 Watlow Anafaze 141
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 51). WatView
software displays a message on the alarm screen and logs
the alarm in the event log.
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
failure.
• The sensor is not placed correctly and is not measuring
the load’s temperature.
• The alarm settings are too tight. The process variable
varies by more than the alarm limits because of load
changes, lag or other system conditions.
• The system is so poorly tuned that the temperature is
cycling 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
risen.
• The heater is full-on because of a hardware failure.
• The system is so poorly tuned that the temperature is
cycling about set point by more than the alarm set
point.
NOTE! In cooling applications, similar issues cause low
alarms.