Fault Finding - Grundfos SEG Instrucciones De Instalación Y Operación

11. Fault finding

Warning
FM
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. 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. Pump operates at below-
standard performance and
increased power
consumption.
5. Pump operates but delivers
no liquid.
6. Pump is blocked.
22
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) Adjustment of 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 under
voltage).
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 Oil
change.
Reduce the liquid temperature.
Dilute the liquid.
Check and correct the electrical
installation.
Clean the impeller.
Check the direction of rotation.
If is not correct, interchange two
phases. See section
9.3 Direction
of rotation.
Check the discharge valve and
open/clean it.
Clean the non-return valve.
Vent the pump.
Replace the grinder system.