English (GB)
18
13. Fault finding
Warning
Before making any connections in pumps, terminal boxes or control cabinet, make sure that the power supply has
been switched off for at least 5 minutes and that it cannot be accidentally switched on.
Fault
Possible cause
Remedy
1. The pumps are not running.
a) Current pressure is higher than or equal
to the setpoint.
Wait until the pressure has dropped, or lower
the pressure on the discharge side of the
booster system, and check that the pumps
start.
b) Power supply disconnected.
Connect the power supply.
c) Main switch cut out.
Cut in the main switch.
d) Main switch is defective.
Replace the main switch.
e) Motor protection is activated.
Contact Grundfos.
f)
Motor is defective.
Repair or replace the motor.
g) Pressure transmitter fault:
• Pressure transmitter is defective.
Replace the pressure transmitter.
0-10 bar or 0- 6 bar transmitters with 0-10 V,
0-20 mA or 4-20 mA output signals are
monitored by the booster system.
h) Cable is broken or short-circuited.
Repair or replace the cable.
2. The pumps start, but stop
immediately.
The operating pressure is not
reached.
a) Water shortage or no inlet pressure.
Re-establish the supply of water to the booster
system. When the inlet pressure has been
re-established, press [Reset] to restart the
system.
3. The booster system is stopped and
cannot restart.
a) Pressure transmitter fault:
• Pressure transmitter is defective.
Replace the pressure transmitter.
0-10 bar or 0-16 bar transmitters with 0-10 V,
0-20 mA or 4-20 mA output signals are
monitored by the booster system.
b) Cable is broken or short-circuited.
Repair or replace the cable.
c) CU 323 fault:
• Power supply is disconnected.
Connect the power supply.
d) The CU 323 is defective.
Contact Grundfos.
4. Unstable water supply from the
booster system.
a) Inlet pressure is too low.
Check the suction pipe and the suction strainer,
if any.
b) Suction pipe or pumps partly blocked by
impurities.
Clean the suction pipes, strainer or pumps.
c) Pumps suck air.
Check the suction pipe for leakages.
d) Pressure transmitter defective.
Replace the transmitter.
5. Pumps are running, but deliver no
water.
a) The valves are closed.
Open the valves.
b) Suction pipe or pumps blocked by
impurities.
Clean the suction pipe or pumps.
c) Non-return valve blocked in closed
position.
Clean the non-return valve. The non-return
valve must move freely.
d) Suction pipe leaky.
Check the suction pipe for leakages.
e) Air in suction pipe or pumps.
Vent and prime the pumps. Check the suction
pipe for leakages.
6. The booster system is unable to
reach the setpoint.
a) Too high consumption.
• Reduce consumption, if possible.
• Install a bigger booster system.
b) Too many standby pumps selected.
Reduce the number of standby pumps.
c) Pipe fracture or leakage in the system.
Check the system, and repair damages,
if necessary.
7. Leakage from the shaft seal.
a) Shaft seal is defective.
Replace the shaft seal.
8. Noise.
a) The pumps are cavitating.
Clean the suction pipe/pumps and possibly the
suction strainer.
9. Very frequent starts and stops.
a) Wrong diaphragm tank precharge
pressure.
Set correct precharge pressure.
