Eng
lish (US)
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 five minutes and that it cannot be accidentally switched on.
Fault
Possible cause
Remedy
The pumps are not running.
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 Hydro Multi-B,
and check that the pumps start.
Power supply disconnected.
Connect the power supply.
Main disconnect switch turned off.
Turn on the main disconnect switch.
Main switch is defective.
Replace the main switch.
Motor protection is activated.
Contact Grundfos.
Motor is defective.
Repair or replace the motor.
The pressure transmitter is defective.
Replace the pressure transmitter.
0-145 psi (0-10 bar) transmitters with 0-10 V,
0-20 mA or 4-20 mA output signals are monitored by
the Hydro Multi-B.
Cable is broken or short-circuited.
Repair or replace the cable.
Incorrect GSC file.
Check if the GSC file is correct by means of a PC Tool.
The pumps start, but stop
immediately.
The operating pressure is not
reached.
Water shortage or no inlet pressure.
Re-establish the supply of water to the Hydro Multi-B.
When the inlet pressure has been re-established,
press [Reset] to restart the system.
The Hydro Multi-B has stopped
and cannot restart.
The pressure transmitter is defective.
Replace the pressure transmitter.
0-145 psi (0-10 bar) transmitters with 0-10 V, 0-20 mA
or 4-20 mA output signals are monitored by the Hydro
Multi-B.
Cable is broken or short-circuited.
Repair or replace the cable.
CU 323 fault:
• Power supply disconnected.
Connect the power supply.
The CU 323 is defective.
Contact Grundfos.
Unstable water supply from the
Hydro Multi-B.
Inlet pressure too low.
Check the suction pipe and the suction strainer, if any.
Suction pipe or pumps partly blocked by
impurities.
Clean the suction pipes, strainer or pumps.
Pumps suck air.
Check the suction pipe for leakages.
Pressure transmitter is defective.
Replace the transmitter.
Incorrect GSC file.
Check if the GSC file is correct by means of a PC Tool.
Pumps are running, but deliver
no water.
The valves are closed.
Open the valves.
Suction pipe or pumps blocked by impurities.
Clean the suction pipe or pumps.
Non-return valve blocked in closed position.
Clean the non-return valve. The non-return valve must
move freely.
Suction pipe leaky.
Check the suction pipe for leakages.
Air in suction pipe or pumps.
Vent and prime the pumps. Check the suction pipe for
leakages.
The Hydro Multi-B is unable to
reach the setpoint.
Too high consumption.
• Reduce consumption, if possible.
• Install a bigger Hydro Multi-B booster system.
Too many standby pumps selected.
Reduce the number of standby pumps.
Pipe fracture or leakage in the system.
Check the system and repair any damage.
Incorrect GSC file.
Check if the GSC file is correct by means of a PC Tool.
Leakage from the shaft seal.
Shaft seal is defective.
Replace the shaft seal.
Noise.
The pumps are cavitating.
Clean the suction pipe/pumps and possibly the suction
strainer.
Very frequent starts and stops.
Wrong diaphragm tank precharge pressure.
Set correct precharge pressure.
