Fault Finding - Grundfos DWK Installation And Operating Instructions Manual

15. Fault finding

Warning
Before starting work on the pump, make
sure that the fuses have been removed or
the mains switch has been switched to off.
Make sure that the power supply cannot
be accidentally switched on.
All rotating parts must have stopped
moving.
For pumps with sensor, start fault finding
by checking the status on the GU01 or
Note
GU02 front panel. See installation and
operating instructions for GU01 or GU02.
Fault Cause
1.
Motor does not
start, fuses blow
2.
or motor
protector trips
immediately. 3.
Caution: Do not
4.
try to start again.
5.
1.
2.
Pump operates,
but motor
protector trips
3.
after a short
4.
while.
1.
The thermal
2.
switch of the
pump trips after a
short while. 3.
1.
Pump operates at
below-standard
2.
performance and
power
consumption.
1.
Pump operates,
2.
but gives no
liquid.
3.
1.
Pump clogged.
2.
Supply failure; short-circuit; earth-
leakage fault in cable or motor
winding.
Fuses blow due to use of wrong type
of fuse.
Impeller blocked by impurities.
Level pickup, float switch or electrode
out of adjustment or defective.
Motor phase malfunction
Low setting of thermal relay in motor
protector.
Increased current consumption due to
large voltage drop.
Impeller blocked by impurities.
Wrong direction of rotation.
Too high liquid temperature.
Inadequate cooling.
Too high viscosity of the pumped
liquid.
Fault in the electrical connection. (Y-
connection of pump to D-connection
results in considerable undervoltage).
Impeller blocked by impurities.
Wrong direction of rotation.
Air in pump.
Outlet valve closed or blocked.
Non-return valve blocked.
The liquid contains large particles.
A float layer has formed on the
surface.
Remedy
Have the cable and motor checked and
repaired by a qualified electrician.
Fit fuses of the correct type.
Clean the impeller.
Check the level pickups, float switches or
electrodes.
Inspect motor and connections.
Set the relay in accordance with the
specifications on the pump nameplate.
Measure the voltage between two motor
phases. Tolerance: - 5 %/+ 5 %.
Clean the impeller.
Check the direction of rotation and possibly
interchange any two phases in the power
supply. See section 12.1 Direction of
rotation.
Improve cooling or lower the liquid
temperature.
Dilute the pumped liquid.
Check and correct the electrical connection.
Clean the impeller.
Check the direction of rotation and possibly
interchange any two phases in the power
supply. See section 12.1 Direction of
rotation.
Vent the pump twice.
Check the outlet valve and possibly open
and/or clean.
Clean the non-return valve.
Select a pump with a larger size of passage.
Install a mixer in the tank.
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