54
Process Value Exceeds Set Point
Probable cause
Remedy
Connections
Process value of the E5ZE is abnormal.
Refer to 4-3 Temperature Sensing Errors for
appropriate troubleshooting.
Load is connected to the incorrect control point of
the E5ZE and is controlling the heaters with the
control output of the incorrect control point.
Correct the wiring of the load.
Relay driven by control output has contact weld.
Replace the relay.
SSR is short-circuited.
Replace the SSR.
SSR leakage current is flowing into the heaters.
Connect a bleeder resistance to the SSR to
prevent operation with the SSR leakage current.
Settings
E5ZE is in reverse operation mode, instead of
direct operation mode, or vice versa.
Correct the operation mode setting.
PID constants of the E5ZE are incorrect.
•
Execute auto-tuning.
•
Set the PID constants of the E5ZE to the values
suitable to the system.
Control output value of the E5ZE does not
increase because of the restrictions of the set
output limit value.
•
Set the output limit value of the E5ZE to an
appropriate value.
Control output value of the E5ZE does not
increase because of the restrictions of the set
output change rate limit value.
•
Disable the output change rate limit function of
the E5ZE by setting to 0000.
•
Set the output change rate limit value of the
E5ZE to an appropriate value.
E5ZE is outputting in manual operation.
Interrupt the manual operation of the E5ZE.
Operation
Controlled object is radiating heat.
Execute heating and cooling control.
Controlled object is influenced by large
overshooting.
Refer to the following table regarding
overshooting and undershooting for appropriate
troubleshooting.
Overshooting or Undershooting
Probable cause
Remedy
Connections
Process value of the E5ZE is abnormal.
Refer to 4-3 Temperature Sensing Errors for
appropriate troubleshooting.
General-purpose temperature sensor with slow
thermal response characteristics is being used to
sense a controlled object with quick thermal
response characteristics.
Change to a sheath-type temperature sensor.
Settings
E5ZE has a narrow proportional band and small
P constant.
•
Increase the P constant keeping within the
range where the response delay caused by the
P constant can be allowed.
•
Execute auto-tuning.
E5ZE has a short integral time or small I
constant.
•
Increase the I constant keeping within the range
where the response delay caused by the I
constant can be allowed.
•
Execute auto-tuning.
E5ZE has a short derivative time or small D
constant.
•
Increase the D constant keeping within the
range where the D constant will not have an
undesirable influence on temperature stability.
•
Execute auto-tuning.
E5ZE is executing ON and OFF control with a P
constant of 0.
Execute P or PID control.
Control period is too long when the E5ZE controls
the temperature of an object with quick thermal
response characteristics.
Shorten the control period.
Dead band instead of an overlap band is set with
the E5ZE in heating and cooling control
operation.
Set the overlap band of the E5ZE.
Temperature Control Errors
Section 4-4
