Grundfos CU 301 Manuel D'instructions page 21

7. Troubleshooting
Before starting any work on the CU 301,
make sure that the electricity supply has
been switched off and that it cannot be
accidentally switched on.
7.1 Service
The CU 301 continuously receives operating data
from the pump. In case of an alarm, the service indi-
cator light is permanently on, see fig. 17.
Fig. 17 Service alarm indicator
The service indicator light will be permanently on if
one of the following alarm situations occurs:
• Sensor defective
• Overload
• Overtemperature
• Speed reduction
• Voltage alarm
• No contact to pump.
To identify the cause of the service alarm, it is
necessary to remove the front cover from the
CU 301 or use the R100. Fit the front cover as
shown in fig. 18 to avoid disconnecting the multi-core
cable.
PSI
100
90
80
70
60
50
40
A number of LEDs are mounted on the supply board
inside the CU 301, see section 4. Position of LEDs.
Fig. 18 LEDs and alarm texts on the supply board
CONTROL INDICATOR
MIN. SPEED
MAX. SPEED
SENSOR DEFECTIVE
OVER LOAD
OVERTEMPERATURE
SPEED REDUCTION
VOLTAGE ALARM
NO CONTACT TO PUMP
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