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Detecting Current Errors Section 4-5
Calculating the Heater
Burnout Detection
Current Value
Calculate the set value with the following equation:
• To set the value of the heater burnout when two or more heaters are con-
nected through the CT, use the current value of the smallest heater con-
nected. (When all of the heaters have the same current value, use the
current value when one of the heaters has burned out.)
• Be sure that the following conditions are satisfied:
Heater with a current of less than 10.0 A:
Current value at normal operation − Current value at heater burnout ≥ 1 A
When the difference is less than 1 A, detection is unstable.
Heater of current 10.0 A or more:
Current value at normal operation − Current value at heater burnout ≥ 2.5 A
When the difference is less than 2.5 A, detection is unstable.
• The setting range is 0.1 to 99.9 A. Heater burnout is not detected when
the setting is 0.0 or 100.0. When the set value is 0.0, the HB alarm is
turned OFF. When the set value is 100.0 the HB alarm is turned ON.
• Set the total current value at normal heater operation to 100 A or less.
Load: Heater (example)
To CT input
AC line
Load
Load
To CT input
CT
CT
Set value =
Normal current value + Burnout current value
2
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