GB
NM-NMD Rev23 - Operating Instructions
Page 13 / 64
12. TROUBLESHOOTING
OFF
WARNING: Turn off the power supply before performing any operations.
Do not allow the pump or motor to run when dry even for a short period.
Strictly follow the user instructions and if necessary contact an authorised service centre.
PROBLEM
PROBABLE CAUSES
POSSIBLE REMEDIES
1)
The motor does
not start
1a) Unsuitable power supply
1b) Incorrect electrical connections
1c) Engine overload protective device cuts
in.
1d) Blown or defective fuses
1e) Shaft blocked
1f) If the above causes have already
been checked, the engine may be
malfunctioning
1a) Check that the mains frequency and voltage correspond to the
electrical characteristics shown on the indicator plate
1b) Connect the power supply cable to the terminal board correctly. Check
that the thermal overload protection is set correctly (see data on the
engine indicator plate) and make sure that the fuseboard upline of the
engine has been properly connected
1c) Check the power supply and make sure that the pump shaft is turning
freely. Check that the thermal overload protection has been set
correctly (see engine indicator plate)
1d) Replace the fuses, check the electric power supply and points a) and c)
1e) Remove the cause of blockage as indicated in the “Blocked pump”
instruction booklet
1f) Repair or replace the engine by applying to an authorised service
centre
2)
Pump blocked
2a) Prolonged periods of inactivity with
formation of rust inside the pump
2b) Presence of solid bodies in the pump
rotor
2c) Bearings siezed
2a) Rotation may be started directly from the pump shaft or from the
joint (remember to turn off the electricity supply first ) or contact an
authorised service centre
2b) If possible, dismantle the pump casing and remove any solid foreign
bodies inside the rotor, if necessary contact an authorised service
centre
2c) If the bearings are damaged replace them or if necessary contact an
authorised service centre
3)
The pump
functions
but no water
comes out
3a) Possible infiltration of air from suction
tube connections, drain plugs or filling
of pump or from the gaskets of the
suction pipe
3b) Foot valve blocked or suction pipe not
fully immersed in liquid
3c) Suction filter blocked
3a) Check which part is not tight and seal the connection adequately
3b) Clean or replace the bottom valve and use a suction pipe suitable for
the application
3c) Clean the filter, if necessary, replace it . See point 2a) also.
4)
Insufficient flow
4a) Pipes and accessories with diameter
too small causing excessive loss of
head
4b) Presence of deposits or solid bodies in
the internal passages of the rotor
4c) Rotor deteriorated
4d) Worn rotor and pump case
4e) Excessive viscosity of the liquid
pumped (if other than water)
4f) Incorrect direction of rotation
4g) Suction head excessive in relation to
the suction capacity of pump
4h) Suction pipe too long
4a) Use pipes and accessories suitable for the specific application
4b) Clean the rotor and install a suction filter to prevent other foreign
bodies from entering
4c) Replace the rotor, if necessary, contact an authorised service centre
4d) Replace the rotor and the pump casing
4e) The pump is unsuitable
4f) Invert the electrical connections on the terminal board or control panel
4g) Try to close the feeder gate partially and/or reduce the difference in
level of the pump and the liquid being aspirated
4h) Bring the pump closer to the suction tank so as to use a shorter pipe.
If necessary use a pipe of a wider diameter
5)
Noise and
vibrations
from the pump
5a) Rotating part unbalanced
5b) Worn bearings
5c) Pump and pipes not firmly attached
5d) Flow too strong for the diameter of the
delivery pipe
5e) Functioning in cavitation
5f) Unbalanced power supply
5g) Incorrect alignment of pump-motor unit
5a) Check that no solid bodies are obstructing the rotor
5b) Replace the bearings
5c) Anchor the delivery and suction piping as needed
5d) Use bigger diameters or reduce the pump flow
5e) Reduce the flow by adjusting the feeder gate and/or using pipes with
a bigger internal diameter. See point 4g) too
5f) Check that the mains voltage is right
5g) If necessary, the unit must be re-aligned
6)
Leakage from
the mechanical
seal
6a) The mechanical seal has functioned
when dry or has stuck
6b) Mechanical seal scored by presence
of abrasive parts in the liquid pumped
6c) Mechanical seal unsuitable for the
type of application
6d) Slight initial drip during filling or on first
start-up
In cases 6a), 6b) and 6c), replace the seal, if necessary contact an
authorised service centre
6a) Make sure that the pump casing (and the suction pipe if the pump is
not self-priming) are full of liquid and that all the air has been expelled.
See point 5 e) too.
6b) Install a suction filter and use a seal suited to the characteristics of the
liquid being pumped.
6c) Choose a seal with characteristics suitable for the specific application
6d) Wait for the seal to adjust to the rotation of the shaft. If the problem
persists, see points 6a), 6b) or 6c) or contact an authorised service centre.
NM-NMD Rev23.indd 13
19/04/17 10:13
