English
12 WILO SE 03/2019
CAUTION! Risk of damage to the installation!
If the initial compressing pressure is poor, the
functioning of the diaphragm pressure vessel
cannot be ensured. This may lead to excessive
wear of the diaphragm and technical failures.
With regards to pressure-boosting systems with
frequency converters, the input and output filters
on the fan must be cleaned as soon as they
become significantly clogged.
When decommissioning the system for a long
period, proceed as described in Section 8.3 and
drain all pumps by opening the drain plugs at the
foot of the pump.
10 Faults, causes and remedies
Troubleshooting, particularly of problems relating
to the pumps and switchgear, must be performed
exclusively by a Wilo customer service agent or a
specialist firm.
NOTICE:
When carrying out all maintenance and repair
work, it is crucial that the general safety instruc
-
tions are observed! It is also important to follow
the installation and operating instructions for the
pumps and switchgear!
DANGER! Risk of fatal injury!
Only specialist and appropriately qualified
personnel may perform troubleshooting!
Observe the safety instructions in Section 9.
Fault Cause Remedies
At least one of the two pumps does
not start
Air intake on suction side Check the impermeability of all connections in the
suction pipework.
Check that the suction strainer is properly submerged
in water.
Foot valve strainer is permeable
or obstructed
Check the impermeability of the valve and replace it
if necessary.
Significant friction losses on the
suction side
Check the friction losses and make sure that they are
compatible with the NPSH of the pumps.
Municipal water supply pressure
too low or zero
Adjust the system to supply the pressure-boosting
system from a replenishment reservoir.
Negative suction head over
reservoir too great
Ensure that the minimum level of the reservoir is
compatible with the pumps’ NPSH.
Suction pipework obstructed or
valve on suction manifold
closed
Check that the valve is open and clean pipework if
necessary.
One pump does not start Thermal motor protection
activated
The pump “malfunction” warning light on the switch
-
gear must be illuminated. Check the thermal motor
protection settings and reset.
Magnetic circuit breaker
activated
Check that the motor phases have not short-
circuited.
Replace the motor if necessary.
Reset the circuit breaker.
Pump shaft blocked Disconnect the switchgear power supply, then check
that the pump shaft turns freely. If it is blocked,
proceed to dismantle the pump.
Winding malfunction Disconnect the terminal of the motor concerned and
check the resistor at the terminals and the stator’s
insulation to earth.
Replace the motor if necessary.
No pressure on the discharge side At least one of the pumps is
deactivated
See the preceding section, fault “At least one of the
two pumps does not start”.
Municipal water supply pressure
below minimum prescribed
pressure
Contact the local water supplier or replace the
pressure-boosting system. Contact us.
One pump is obstructed by
foreign bodies
Dismantle and clean the pump.
The motors are supplied by
insufficient power supply
voltage
Check the voltage and the connection to motor
terminals.
Random operation, pumps start
frequently
Pressure sensor is defective Check settings: if sensor is unstable, it must be
replaced.
Insufficient system capacity
(or tank of insufficient capacity)
Install an additional storage tank or replace with a
tank that has greater capacity.
Tank pre-inflation level does
not conform
Proceed to inflate the tank.
Water storage vessel pierced Replace the vessel.
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