Fault Finding The Product - Grundfos DP 10 Installation And Operating Instructions Manual

9. Fault finding the product

Before attempting to diagnose any fault, read and
observe the safety instructions in section
instructions and requirements.
Observe all regulations applying to pumps
installed in potentially explosive
environments.
Make sure that no work is carried out in a
potentially explosive atmosphere.
Fault
1. The pump does not
start. The fuses blow or
the motor-protective
circuit breaker trips
immediately.
Caution: Do not start
again!
2. The pump starts, but
the motor-protective
circuit breaker trips after
a short time.
3. The pump's thermal
switch trips after the
pump has been running
for some time.
4. The pump runs at
below-standard
performance and power
consumption.
5. The pump runs, but
delivers no liquid.
26
8.1 Safety
Cause
a) Power supply failure, short circuit
or earth leakage in the power
cable or the motor windings.
b) Wrong type of fuse.
c) The impeller is blocked by
impurities.
d) The air bells, the float switches or
the electrodes are 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) The liquid temperature is too high. Reduce the liquid temperature.
b) The liquid viscosity is too high.
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) The direction of rotation is wrong.
a) The outlet valve is closed or
blocked.
b) The non-return valve is blocked.
c) There is air in the pump.
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.
Remedy
Have the power 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 8.5 Adjusting the
impeller clearance.
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
in the power cable. See section
4.3 Direction of rotation.
Check the outlet valve and open and/
or clean it, if necessary.
Clean the non-return valve.
Vent the pump.