Grundfos CRN 125-11, Installation And Operating Instructions Manual

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Cause Remedy
The main contacts in
the motor-protective
circuit breaker are not
making contact or the
coil is faulty. Replace the contacts or
the magnetic coil.
The control circuit is
defective. Repair the control circuit.
8.5 The pump performance is not constant.
Cause Remedy
The pump inlet pressure
is too low (cavitation). Check the inlet conditions.
The inlet pipe or pump
is partly blocked by
impurities. Clean the inlet pipe or
pump.
The pump draws in air. Check the inlet conditions.
8.6 The pump runs, but gives no water.
Cause Remedy
The inlet pipe or pump
is blocked by impurities. Clean the inlet pipe or
pump.
The foot or non-return
valve is blocked in
closed position. Repair the foot or non-
return valve.
There is a leakage in
the inlet pipe. Repair the inlet pipe.
There is air in the inlet
pipe or pump. Check the inlet conditions.
The motor runs in the
wrong direction of
rotation. Change the direction of
rotation of the motor.
8.7 The pump runs backwards when
switched off.
Cause Remedy
There is a leakage in
the inlet pipe. Repair the inlet pipe.
The foot or non-return
valve is defective. Repair the foot or non-
return valve.
8.8 Leakage in the shaft seal.
Cause Remedy
The shaft seal is
defective. Replace the shaft seal.
8.9 Noise.
Cause Remedy
Cavitation. Check the inlet conditions.
The pump does not
rotate freely due to
frictional resistance as a
result of incorrect pump
shaft position. Adjust the pump shaft as
described in the service
documentation. See the
section on service
documentation.
Frequency converter
operation. See the instructions for the
motor which are supplied
with the pump.
29
English (GB)