20
Fault Possible cause Remedy
1. No light in the
front cover.
a) The multi-core
connection is mis-
placed or defec-
tive.
• Is the control indicator LED flashing?
If not, the CU 301 is defective.
• Check that the multi-core cable connection is OK.
If so, the CU 301 is defective.
2. The pump does
not start.
The green indi-
cator light in the
on/off button is
on.
No alarm is in-
dicated.
a) The CU 301 or
the pump is de-
fective.
Check
• that the control indicator LED is flashing.
If not, the CU 301 is defective.
• that the system pressure is 0.5 bar below the pressure set-
ting.
If so, the pump is supposed to start. Open a tap to be sure.
If the pump starts, the system is probably OK.
The system pressure can be read on the pressure gauge.
• See point 13. to check the pressure sensor.
If the pump has not started yet, proceed as follows:
• Press the on/off button for 5 seconds.
If the pump starts, the CU 301 or the sensor may be defective.
Note: The pressure is not controlled and may rise to a high
level.
3. The pressure is
not constant.
a) The pump is not
of the correct type
or the precharge
pressure of the
diaphragm tank is
incorrect.
Check
• that the LED for Max. speed or Min. speed is on.
If so, this indicates that the pump has reached a limit.
See section 1.3 System sizing.
Replace the pump, if necessary.
• the precharge pressure of the diaphragm tank.
Note: Remember to stop and drain the system before the
pressure is checked.
• whether the sensor is positioned far away from the tap.
If so, the pressure variations may be caused by friction
losses, see section 1.4 Positioning the pressure sensor.
4. The pump is
running con-
tinuously.
a) The pump cannot
deliver the pres-
sure set.
The CU 301 or
the sensor is de-
fective.
• Try to lower the pressure set, see section 1.3 System sizing.
Note that the pump may run for about 15 to 20 seconds be-
fore it stops.
• Check that the control indicator LED is flashing.
• Check that the pipe end of the sensor is not blocked.
If so, remove the blockage.
• Try to stop the pump by means of the on/off button.
If this is not possible, the CU 301 is defective.
Replace the CU 301.
• See point 13. to check the pressure sensor.
(continued on the following pages)
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