English (GB)
21
11. Fault finding
Before attempting to diagnose any fault,
– make sure that the fuses have been
removed or the main switch has
been switched off
– make sure that the power supply
cannot be accidentally switched on
– make sure that all rotating parts have
stopped moving.
Observe all regulations applying to pumps
installed in potentially explosive
environments.
Make sure that no work is carried out in
potentially explosive atmosphere.
Fault
Cause
Remedy
1.
The motor does not
start. The fuses blow or
the motor-protective
circuit breaker trips
immediately.
Caution:
Do not start
again!
a)
Supply failure, short-circuit or
earth-leakage fault in the cable or
motor winding.
Have the cable and motor checked
and repaired by a qualified
electrician.
b)
The fuses blow due to use of
wrong type of fuse.
Install fuses of the correct type.
c)
The impeller is blocked by
impurities.
Clean the impeller.
d)
Air bells, float switches or
electrodes are out of adjustment
or defective.
Readjust or replace the air bells,
float switches or electrodes.
2.
The pump operates, but
the motor-protective
circuit breaker trips after
a short while.
a)
Low setting of the thermal relay in
the 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 %.
Reestablish correct voltage supply.
c)
The impeller is blocked by
impurities. Increased current
consumption in all three phases.
Clean the impeller.
d)
The impeller clearance is
incorrect.
Readjust the impeller.
See section
, fig.
.
3.
The pump's thermal
switch trips after the
pump has been
operating for some
time.
a)
The liquid temperature is too high. Reduce the liquid temperature.
b)
The liquid viscosity is too high.
Dilute the liquid.
c)
Wrong electrical connection. If the
pump is star-connected to a delta
connection, the result will be very
low undervoltage.
Check and correct the electrical
installation.
4.
The pump operates at
below-standard
performance and power
consumption.
a)
The impeller is blocked by
impurities.
Clean the impeller.
b)
The direction of rotation is wrong.
Check the direction of rotation and
possibly interchange any two phases
of the incoming power cable. See
section
.
5.
The pump operates, but
delivers no liquid.
a)
The outlet valve is closed or
blocked.
Check the outlet valve and possibly
open and/or clean it.
b)
The non-return valve is blocked.
Clean the non-return valve.
c)
There is air in the pump.
Vent the pump.
