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18
11. Fault finding
Warning
Before attempting to diagnose any fault, make sure that the fuses have been removed or the
mains switch has been switched off. Make sure that the power supply cannot be accidentally
switched on.
All rotating parts must have stopped moving.
Fault
Cause
Remedy
1.
Motor does not start.
Fuses blow, or
motor-protective circuit
breaker trips immediately.
Caution:
Do not start again!
a)
Supply failure; short-circuit;
earth-leakage fault in cable or
motor winding.
Have the cable and motor checked
and repaired by a qualified
electrician.
b)
Wrong type of fuse.
Install fuses of the correct type.
c)
Impeller blocked by impurities.
Clean the impeller.
d)
Air bell, float switch or
electrode out of adjustment or
defective.
Check the air bells, float switches
or electrodes.
2.
Pump runs, but the motor-
protective circuit breaker
trips after a short while.
a)
Low setting of thermal relay in
motor-protective circuit
breaker.
Set the relay in accordance with
the specifications on the
nameplate.
b)
Increased current consumption
due to large voltage drop.
Measure the voltage between two
motor phases.
Tolerance: - 10 %/+ 6 %.
c)
Impeller blocked by impurities.
Increased current consumption
in all three phases.
Clean the impeller.
d)
Adjustment of impeller
clearance incorrect.
Readjust the impeller. See fig. 12 in
section
3.
The pump’s thermal switch
trips when the pump has
been operating for some
time.
a)
Too high liquid temperature.
Reduce the liquid temperature.
b)
Too high liquid viscosity.
Dilute the liquid.
c)
Wrong electrical connection.
(If the pump is star-connected
to a delta connection, the
result will be very low under
voltage).
Check and correct the electrical
installation.
4.
Pump operates at below-
standard performance and
increased power
consumption.
a)
Impeller blocked by impurities. Clean the impeller.
Check the direction of rotation. If is
not correct, interchange two
phases. See section
.
b)
Wrong direction of rotation.
5.
Pump runs but gives no
liquid.
a)
Discharge valve closed or
blocked.
Check the discharge valve and
open/clean it.
b)
Non-return valve blocked.
Clean the non-return valve.
Vent the pump.
c)
Air in pump.
6.
Pump is blocked.
a)
Grinder system is worn.
Replace the grinder system.
