Fault Finding - Grundfos SEG Serie Montage- Und Betriebsanleitung

11. Fault finding

Warning
All regulations applying to pumps installed in potentially explosive environments must be
observed.
Make sure that no work is carried out in potentially explosive atmosphere.
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
1. Motor does not start.
Fuses blow, or motor-
protective circuit breaker
trips immediately.
Caution: Do not start again!
2. The pump operates, but the
motor-protective circuit
breaker trips after a short
while.
3. The pump's thermal switch
trips when the pump has
been operating for some
time.
4. The pump operates at
below-standard
performance and increased
power consumption.
5. The pump operates but
delivers no liquid.
6. The pump is blocked.
Cause
a) Supply failure; short-circuit;
earth-leakage fault in cable or
motor winding.
b) Wrong type of fuse.
c) Impeller blocked by impurities.
d) Air bell, float switch or
electrode out of adjustment or
defective.
a) Low setting of thermal relay in
motor-protective circuit
breaker.
b) Increased current consumption
due to large voltage drop.
c) Impeller blocked by impurities.
Increased current consumption
in all three phases.
d) Impeller clearance incorrect.
a) Too high liquid temperature.
b) Too high liquid viscosity.
c) Wrong electrical connection.
(If the pump is star-connected
to a delta connection, the result
will be very low undervoltage).
a) Impeller blocked by impurities.
b) Wrong direction of rotation.
a) Discharge valve closed or
blocked.
b) Non-return valve blocked.
c) Air in pump.
a) Grinder system is worn.
Remedy
Have the cable and motor checked
and repaired by a qualified
electrician.
Install fuses of the correct type.
Clean the impeller.
Check the air bells, float switches
or electrodes.
Set the relay in accordance with the
specifications on the nameplate.
Measure the voltage between two
motor phases.
Tolerance: - 10 %/+ 6 %.
Clean the impeller.
Readjust the impeller.
See fig. 12 in section 10.2.
Reduce the liquid temperature.
Dilute the liquid.
Check and correct the electrical
installation.
Clean the impeller.
Check the direction of rotation.
If it is not correct, interchange two
phases. See section 9.3 Direction
of rotation.
Check the discharge valve and
possibly open and/or clean it.
Clean the non-return valve.
Vent the pump.
Replace the grinder system.
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