Grundfos CRK Series, Installation And Operating Instructions Manual

Page: 14 / 108

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12. Fault finding
Warning
Before starting work on the pump, make
sure that all power supplies to the pump
have been switched off and that they
cannot be accidentally switched on.
Fault Cause Remedy
1. Motor does not run
when started. a) Power supply failure. Connect the power supply.
b) Fuses are blown. Replace fuses.
c) Motor-protective circuit breaker has
tripped out. Reactivate the motor-protective
circuit breaker.
d) Thermal protection has tripped out. Reactivate the thermal protection.
e) Main contacts in motor-protective
circuit breaker are not making contact
or the coil is faulty. Replace contacts or magnetic coil.
f) Control circuit is defective. Repair the control circuit.
g) Motor is defective. Replace the motor.
2. Motor-protective
circuit breaker trips
out immediately
when power supply
is switched on. a) One fuse blown/automatic circuit
breaker has tripped out.
Replace fuse/cut in the circuit
breaker.
b) Contacts in motor-protective circuit
breaker are faulty.
Replace motor-protective circuit
breaker contacts.
c) Cable connection is loose or faulty. Fasten or replace the cable
connection.
d) Motor winding is defective. Replace the motor.
e) Pump mechanically blocked. Remove the mechanical blocking of
the pump.
f) Motor-protective circuit breaker
overload setting is too low. Set the motor-protective circuit
breaker correctly.
3. Motor-protective-
circuit breaker trips
out occasionally. a) Motor-protective circuit breaker
overload setting is too low.
Set the motor-protective circuit
breaker correctly.
b) Low voltage at peak times. Reestablish constant power supply.
4. Motor-protective-
circuit breaker has
not tripped out but
the pump does not
run. a) Check 1 a), b), d), e) and f).
5. Pump runs but
gives no liquid or
pump performance
is not constant. a) Pump strainer partly blocked by
impurities.
Clean the strainer.
b) Liquid level in tank too low. Increase the liquid level.
c) Pump draws in air. Check the suction conditions.
6. Leakage in shaft
seal. a) Shaft seal is defective.
Replace the shaft seal.
7. Noise. a) Cavitation. Check the suction conditions.
b) Pump does not rotate freely (frictional
resistance) because of incorrect
pump shaft position. Adjust the pump shaft.
c) Frequency converter operation. See section 7.1 Frequency converter
operation .