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8-1 Heater Burnout Detection
To detect heater burnout, wire one of the lead wires for each heater through the
hole of the Current Transformer (CT). The CT generates an AC current accord-
ing to the current flow of the lead wire. The Thermac E5J Temperature Control-
ler measures the AC current to check the current flowing to the heater. If any one
of the heaters burns out, the AC current value will decrease so that the E5J
turns its heater burnout alarm ON, comparing the AC current value with the heat-
er burnout alarm value.
8-2 Heater Burnout Procedures
The E5J starts heater burnout detection from the moment the E5J is turned
on. If any one of the heaters is turned on after the E5J is turned on, the heater
burnout alarm output will be ON because the E5J judges that the heater is
burnt out. Therefore, all the heaters must be turned on simultaneously with the
E5J or before the E5J is turned on. This is essential for smooth temperature
control and fuzzy self-tuning.
The E5J will continue temperature control even if the heater burnout alarm is
ON because the E5J will continue temperature control using the heaters that
are not burnt out.
Heater burnout detection is possible when the control output is ON. No heater
burnout detection is, however, possible if the control output is ON for less than
190 ms.
The heater burnout alarm output will be held once the heater burnout is de-
tected. To reset the heater burnout alarm output, replace the burnout heater with
a good one and take one of the following steps.
1, 2, 3...
1. Set the heater burnout alarm value to 0.0 A.
2. Turn the E5J off and on.
If the difference between the normal heater current value and heater burnout
current value is comparatively small, heater burnout detection will not be stable.
For stable detection, the difference must be 1.0 A minimum if the heater current
consumption is less than 10.0 A and 2.5 A minimum if the heater current con-
sumption is 10.0 A or more.
Heater burnout detection is not possible if the E5J has current output, the
heater current is DC, or three-phase heaters are used.
Use the K2CU-FA-GS (with gate input terminals) for three-phase heater
burnout. Refer to the K2CU-FA-GS data sheet specifications for details.
If no heater burnout detection is executed or if no CT is used, set the heater burn-
out alarm value to 0.0 A. The heater burnout alarm value is factory-set to 0.0 A.
Heater Burnout Procedures
Section 8-2
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