Q Nom; Fault Finding 10 Fig; Notes Or Instructions That Make The Job Easier; And Ensure Safe Operation - Grundfos CM SP Service Instructions Manual

6. Fault finding
Warning
Before removing the terminal box cover, make sure that the power supply has been switched off. Make sure that it
cannot be accidentally switched on.
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.
Fault
1. The pump does not run.
2. Motor-protective circuit breaker has
tripped (trips out immediately when
supply is switched on).
3. The motor-protective circuit breaker
trips out occasionally.
4. The motor-protective circuit breaker
has not tripped out, 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.
7. The pump runs, but gives no water.
8. When startup is attempted, the pump
will start, but delivers no pressure or
flow.
10
Cause
a) Supply failure.
b) Fuses are blown.
c) Motor protection tripped.
d) Control-current circuit defective.
a) Fuses are blown.
b) Contacts of the motor-protective circuit
breaker or magnet coil defective.
c) Cable connection is loose or faulty.
d) Motor winding is defective.
e) Pump is mechanically blocked.
f) Setting of motor-protective circuit
breaker is too low.
a) Setting of motor-protective circuit
breaker is too low.
b) Periodic supply failure.
c) Periodically low voltage.
a) See 1. a), b), d) and 2. e).
a) Pump inlet pressure is 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.
a) Pump inlet pressure is too low.
b) Suction pipe is partly clogged by
impurities.
c) The foot or non-return valve is stuck in
its closed position.
d) Leakage in suction pipe.
e) Air in suction pipe or pump.
Self-priming pumps only:
a) Liquid column above non-return valve in
discharge pipe prevents the pump from
self-priming.
b) Suction pipe draws in air.
Remedy
Switch on the switch.
Check cables and cable connections for
defects and loose connections.
Check cables and cable connections for
defects, and replace the fuses.
See 2. a), b), c), d), e), f).
Repair or replace the control-current circuit.
See 1. b).
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.
1/1
See 2. f).
See 2. c).
Check cables and cable connections for
defects and loose connections.
Check that the 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/pump.
Check the inlet conditions of the pump.
Close the tap gradually until the discharge
pressure is stable and the noise has ceased.
See 5. a).
See 5. b).
Remove and clean, repair or replace the valve.
See 5. c).
See 5. d).
Empty the discharge pipe. Make sure that the
non-return valve does not hold back liquid in
the discharge pipe. Repeat the startup
procedure described in the installation and
operating instructions.
Make sure that the suction pipe is airtight from
pump to liquid level. Repeat the startup
procedure described in the installation and
operating instructions.