Grundfos CU 301 Installation And Operating Instructions Manual page 26

Fault Possible cause
12 CU 301 indicates a)
"Overload".
b)
13 CU 301 indicates a)
"Sensor defective".
14 The pump is a)
operating on and
off.
Related information
2.3 Positioning the pressure sensor
3.2 System sizing
4.6 Service alarm
4.8 Position of LEDs
5.3.7 Dry-running stop
5.3.11 Number
8. Technical data
26
The pump is worn or blocked.
The pump is too large for the
installed motor.
The pressure sensor is
defective.
No communication.
Remedy
The pump must be serviced.
Replace the pump or motor.
Check that the sensor is installed correctly.
Check that the Grundfos GO Remote setting of the sensor is
correct.
If the sensor type is 4-20 mA, measure the signal current.
If the current is above 2 mA, the sensor and wiring are OK.
If the current is below 2 mA, the sensor or wiring is defective.
Replace defective parts.
Are the LED "Sensor defective" and the LED, pos. 1, on? See
section 4.8 Position of LEDs.
• Yes: The total load of 24 VDC from terminal 5 is above 100
mA.
Disconnect the sensor in order to determine if it is
defective.
Replace defective sensor.
• No: The load is OK, but the CU 301 sensor input may be
defective.
Check that the LED "No contact to pump" is on.
If so, CU 301 starts and stops the pump, based on the sensor
signal only. CU 301 has to be reset every 250 stops.
Refer to fault no. 5 for remedy.