52
The normal heater current value should be 50.0 A max. The heater current value
can, however, display up to 55.0 A. If the current value exceeds 55.0 A, CT input
overflow will result and
ffff
will be displayed.
CT input
overflow
8-4-1 Setting Examples
Example 1
In this example, 1-kW, 2-kW, and 3-kW heaters at 200 VAC are connected in par-
allel.
1, 2, 3...
1. Turn the control output ON and check the normal heater current value from
the heater current value display.
Normal current = (1000 + 2000 + 3000)
200 = 30.0 A
Heater current value display
Normal heater
current value
200 VAC
CT
1KW 2KW 3KW
Heater
Control
output ON
2. Disconnect the heater whose current consumption is smallest and compare
the heater current value from the heater current value display.
Heater burnout current = 30.0 – 1000
200
25.0 A
Heater
Control
output ON
200 VAC
CT
1KW 2KW 3KW
Disconnect
Heater current value display
Heater burnout
current value
Normal current – heater burnout current = 30.0 – 25.0 = 5 A (
2.5 A)
3. Set the heater burnout alarm value to the mean value of the normal current
value and heater burnout current value.
Heater burnout alarm value = (30.0 + 25.0)
2 = 27.5 A
Example 2
In this example, 400-W, 1700-W, and 2000-W heaters at 200 VAC are con-
nected in parallel and the difference between the normal current value and heat-
er burnout current value is less than 2.5 A.
1, 2, 3...
1. Obtain the normal current value and heater burnout current value in ad-
vance as follows:
Normal current = (400 + 1700 + 2000)
200 = 20.5 A
Heater burnout current = 20.5 – 400
200 = 18.5 A
Normal current – heater burnout current = 20.5 – 18.5 = 2.0 A (Stable detec-
tion is not possible because the value is not 2.5 A or more.)
2. For stable hater burnout detection, in such a case, increase the number of
turns of the wire passing through the CT as if apparent current value in-
Heater Burnout Alarm Value
Section 8-4
