Fault Finding - Grundfos SEG Instrucciones De Instalación Y Funcionamiento

12. Fault finding

Warning
All regulations applying to pumps installed in
FM
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. The motor does not start. The fuses
blow, or the motor-protective circuit
breaker trips immediately.
Caution: Do not start again!
2. The pump runs, 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 runs but gives no liquid.
6. The pump is blocked.
18
Cause
a) Supply failure; short-circuit; earth-
leakage fault in the cable or the motor
winding.
b) Wrong type of fuse.
c) The impeller is blocked by impurities.
d) The float switch is out of adjustment or
defective.
a) Low setting of the thermal relay in the
motor-protective circuit breaker.
b) Increased current consumption due to
large voltage drop.
c) The impeller is blocked by impurities.
Increased current consumption in all
three phases.
d) Adjustment of the 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) The impeller is blocked by impurities.
b) Wrong direction of rotation.
a) The outlet valve is closed or blocked.
b) The non-return valve blocked.
c) Air in the pump.
a) The grinder system is worn.
Remedy
Have the cable and the motor checked and
repaired by a qualified electrician.
Install fuses of the correct type.
Clean the impeller.
Check the float switches.
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
11.4 Adjustment of impeller clearance.
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
10.3 Direction of rotation.
Check the outlet valve and open or clean it.
Clean the non-return valve.
Vent the pump.
Replace the grinder system.
in section