Fault Finding - Grundfos DP 10 Serie Montage- Und Betriebsanleitung

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
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 operates, but
the motor-protective
circuit breaker trips after
a short while.
3. The pump's thermal
switch trips after the
pump has been
operating for some
time.
4. The pump operates at
below-standard
performance and power
consumption.
5. The pump operates, but
delivers no liquid.
24
Cause
a) Supply failure, short-circuit or
earth-leakage fault in the cable or
motor winding.
b) The fuses blow due to use of
wrong type of fuse.
c) The impeller is blocked by
impurities.
d) Air bells, float switches or
electrodes 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) The impeller clearance is
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 is blocked.
c) Air in the pump.
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.
Remedy
Have the cable and motor checked
and repaired by a qualified
electrician.
Install fuses of the correct type.
Clean the impeller.
Readjust or replace 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 %.
Reestablish correct voltage supply.
Clean the impeller.
Readjust the impeller.
See section 10.2 Adjusting the
impeller clearance, fig. 11.
Reduce the liquid temperature.
Dilute the liquid.
Check and correct the electrical
installation.
Clean the impeller.
Check the direction of rotation and
possibly interchange any two phases
of the incoming supply cable. See
section 9.3 Direction of
Check the outlet valve and possibly
open and/or clean it.
Clean the non-return valve.
Vent the pump.
rotation.