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Symptom. Temperature overshoots, or
oscillates
Check - Check bandwidth
Loose heater or sensor t. Poor relative location.
Probable Cause.
- Process overpowered
- Bandwidth too narrow
- Process or sensor lag
Corrective Action
- Reduce total heater power
- Widen band
- Improve t, locate closer together
Symptom. Process control temperature
stabilizes above or below set- point as
read on deviation meter
Check - Oset (manual reset) Heater to ground resistance.
Design parameters for process heat required
Probable Cause.
- Oset (manual reset) incorrectly adjusted
- Partial short to ground in heater when
used on 240 V line
- No output from suspect control
- Controller reading other zones of multi-
controlled process
- Full output from suspect control
- Apparent stabilization from other zones of
multi-controlled process
- Improperly sized heater
Corrective Action
- Adjust (+) to increase controlled temp. (-) to decrease temp.
- Replace defective heater