Setting The Heating Current Monitoring - Nordmann AT4 D Service Manual

2.6

Setting the heating current monitoring

Select "Overcurrent" in the engineering menu, then press the <Set> key.
Engineering
Drain Cool :On
GFCI :Set
Overcurrent :Float
Min.Request :25/20%
Stop Mode :Set
Esc
In the upcoming modification dialogue you determine whether the current monitoring shall take place
with a fixed (Fixed) or a floating over current threshold (Float).
Factory setting:
Setting range:
Notes on settings
For the heating current monitoring, there are two over current thresholds:
– The threshold for the
dashed line in the following diagram). This threshold value is fixed and leads always to a draining
of the cylinder and to an emergency shut-down (Error E25) when exceeded.
– The threshold for the
this threshold value is exceeded the unit tries to reduce the current under 125 % by repetitive drain-
ings. If after 5 repetitive drainings the current value is still above the threshold value of 125 % the
unit goes on error (Error 24).
This threshold is fixed based on the maximum nominal current if
tinuous line in the following diagram).
With the function
can be flattened. The function Float allows a faster reaction to changes of the control signal.
Draining characteristics with over current
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
20 25 30 35 40
Nominal current 100%
Current setpoint value
Draining if current value exceeds the set point value by a factor of 1.5 (setting "Float")
Draining if current value reaches 125 % of the maximum nominal current value (setting "Fixed")
Forced draining if current value reaches 135 % of maximum nominal current value
8
Overcurrent
Float
Fixed
Float
Set Esc Set
Float
Float (floating over current threshold) or
excess current
over current
Float the over current threshold (red, dash-dotted line in the following diagram)
45 50 55 60 65
Steam production demand in %
Fixed
is set to 135% of the maximum nominal current (violet, narrow
is set to 125% of the maximum nominal current (W24/E24). If
70 75 80 85 90 95
(fixed over current threshold)
Fixed is selected (light
Example:
Nominal current at 100% steam pro-
duction with 400V 10kg/h = 10 A
Actual steam demand 30%
––> Current setpoint value = 3 A
Draining as a result of over current at
4.5 A with setting "float"
Draining as a result of over current at
12.5 A with setting "Fixed"
100
blue, con-