Fault Finding Chart - Grundfos DNP series Montage- Und Betriebsanleitung

10. Fault Finding Chart

Before removing the terminal box cover and before any removal/dismantling of the pump, make sure that the electricity supply
has been switched off and that it cannot be accidentally switched on.
Fault
1. Motor does not run when started.
2. Motor starter overload trips out imme-
diately when supply is switched on.
3. Motor starter overload trips out occa-
sionally.
4. Motor starter has not tripped out but
the pump does not run.
5. Pump capacity not constant.
6. Pump runs but gives no water.
7. Pump runs backwards when switched
off.
8. Leakage in shaft seal.
9. Noise.
10. Pump runs constantly (applies only to
pumps with automatic start/stop).
11. Period of operation is too long
(applies only to pumps with automatic
start/stop).
Cause
a) Supply failure.
b) Fuses blown.
c) Motor starter overload has tripped out.
d) Main contacts in motor starter are not making contact or the coil is faulty.
e) Control circuit fuses are defective.
f) Motor is defective.
a) One fuse is blown.
b) Contacts in motor starter overload are faulty.
c) Cable connection is loose or faulty.
d) Motor winding is defective.
e) Pump mechanically blocked.
f) Overload setting too low.
a) Overload setting too low.
b) Supply voltage periodically too low or too high.
c) Differential pressure across pump too low, see section 7.3 Starting .
a) Check 1 a), b), d) and e).
a) Pump inlet pressure is too low.
b) Suction pipe/pump partly blocked by impurities.
c) Pump draws in air.
a) Suction pipe/pump blocked by impurities.
b) Foot or non-return valve blocked in closed position.
c) Leakage in suction pipe.
d) Air in suction pipe or pump.
e) Motor rotates in the wrong direction.
a) Leakage in suction pipe.
b) Foot or non-return valve defective.
c) Foot or non-return valve blocked in open or partly open position.
a) Pump shaft position is incorrect.
b) Shaft seal is defective.
a) Cavitation occurs in the pump.
b) Pump does not rotate freely (frictional resistance) because of incorrect pump shaft
position.
c) Frequency converter operation:
– See section 6.1 Frequency Converter Operation .
– Resonance in the installation.
d) Foreign bodies in the pump.
a) The stop pressure has been set too high.
b) The water consumption is larger than anticipated.
c) Leakage in discharge pipe.
d) The direction of rotation of the pump is incorrect.
e) Pipes, valves or strainer blocked by impurities.
f) Pump controller, if fitted, is defective.
a) The stop pressure has been set too high.
b) Pipes, valves or strainer blocked by impurities.
c) Pump partly blocked or furred up.
d) The water consumption is larger than anticipated.
e) Leakage in discharge pipe.
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