Grundfos ALR 20/A Ex Instrucciones De Instalación Y Funcionamiento página 8

3.2.4 Setting the switch point
CAUTION
Electric shock
Minor or moderate personal injury
- When the power supply is on, the
settings of the switch point must only be
conducted with suitable and isolated
tool.
The switch point has to be set after every connection
or re-connection of the leakage sensor to the
ALR 20/A Ex.
Proceed as follows, see fig. 3:
1. Turn the adjusting screw (2) on top of the
ALR 20/A Ex housing counter clockwise until the
indicator light (4) is on (indicator light signalling a
fault).
2. Turn the adjusting screw (2) slowly in the
opposite direction until the indicator light (4) is
off.
3. Continue turning the adjusting screw (2)
approximately a quarter (from 60 ° to 90 °) in the
same direction as under step 2.
3.2.5 Testing the leakage sensor
Two wires lead from ALR 20/A Ex to the sensor; they
supply the sensor and also lead a variable current
signal, depending on the amount of water in the gear
oil. This current measured by the ALR 20/A Ex
decreases as the amount of water in the oil
increases and it will be compared with a manually
adjustable switch point. If the limit of this switch point
is exceeded, the relay will switch to "error" mode.
Also, in case of a short circuit or a cable break the
relay will automatically switch to "error" mode.
Testing with connected ALR 20/A Ex
In order to test the status or the functionality of the
leakage sensor and the ALR 20/A Ex, the current
flowing through the sensor must be measured. See
fig. 2.
The table below helps to make a conclusion
depending on the current measured:
Current
Meaning
[mA]
No floating
< 0.5
current
Low
0.5 - 5
current
Normal
5-11
current
Too high
> 11
current
* Depending on switch point setting
8
Relay
Cause
status
Break of power
Error
cable
Sensor detects
Error
water in oil
Sensor detects
few water or no *
water in oil
Short circuit in
Error
power cable
L N
5 A
250 V
A
Fig. 2 Wiring for testing with ALR 20/A Ex