Fault Finding - Grundfos CM Montage- Und Betriebsanleitung

12. Fault finding

Warning
Before removing the terminal box cover,
switch off the power supply. Make sure
that the power supply cannot be
accidentally switched on.
Fault
1. The pump does not run.
2. Motor-protective circuit
breaker has tripped (trips
immediately when power
supply is switched on).
3. The motor-protective circuit
breaker trips occasionally.
4. The motor-protective circuit
breaker has not tripped, but
the pump is inadvertently
out of operation.
5. The pump performance is
unstable.
6. The pump performance is
unstable, and the pump is
noisy.
Cause
a) Supply failure.
b) Motor protection tripped.
c) Control-current circuit
defective.
a) Contacts of the
motor-protective circuit
breaker or magnet coil
defective.
b) Cable connection is loose or
faulty.
c) Motor winding is defective.
d) The pump is mechanically
blocked.
e) The setting of the
motor-protective circuit
breaker is too low.
a) The setting of the
motor-protective circuit
breaker is too low.
b) Periodic supply fault.
c) Periodically low voltage.
a) See 1. a), b), c) and 2. d).
a) Pump inlet pressure too low.
b) Suction pipe is partly blocked
by impurities.
c) Leakage in suction pipe.
d) Air in suction pipe or pump.
Self-priming pumps only:
a) The differential pressure
across the pump is too low.
Warning
The pumped liquid may be scalding hot
and under high pressure. Before any
removal or dismantling of the pump, the
system must therefore be drained, or the
isolating valves on either side of the pump
must be closed.
Remedy
Switch on the switch.
Check cables and cable connections
for defects and loose connections.
See 2. a), b), c), d), e).
Repair or replace the control-current
circuit.
Replace the contacts of the
motor-protective circuit breaker, the
magnet coil or the entire
motor-protective circuit breaker.
Check cables and cable connections
for defects, and replace the fuses.
Repair or replace the motor.
Switch off the power supply, and
clean or repair the pump.
Set the motor-protective circuit
breaker according to the rated
current of the motor (I
See nameplate.
See 2. e).
See 2. b).
Check cables and cable connections
for defects and loose connections.
Check that the power supply cable of
the pump is correctly sized.
Check the inlet conditions of the
pump.
Remove and clean the suction pipe.
Remove and repair the suction pipe.
Vent the suction pipe or pump.
Check the inlet conditions of the
pump.
Close the tap gradually until the
discharge pressure is stable and the
noise has ceased.
).
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