Cause Remedy
The shaft is bent due to damage.
• Check the deflection of the shaft. The total indicator
runout must not exceed 0.05 mm.
• Possibly replace the shaft.
Mechanical failure of bearing and/or impeller.
• Check the bearings and the impeller for damage.
• Replace the bearings or the impeller, if necessary.
Misalignment.
• Realign the pump and the motor.
Electrical defects.
• Check that the voltage and frequency of the power
supply are correct.
• Remedy the possible defects in the motor.
• Check that the motor is properly cooled.
The speed is too high.
• Check that the frequency of the power supply
corresponds to the frequency stated on the motor
nameplate.
8.6 The motor is overloaded
Cause Remedy
The viscosity or specific gravity of the pumped liquid
is higher than that of water.
• Use a larger motor. Consult Grundfos for
recommended size.
• Test the liquid for viscosity and specific gravity.
The shaft is bent due to damage.
• Check the deflection of the shaft. The total indicator
runout must not exceed 0.05 mm.
• Possibly replace the shaft.
Mechanical failure of bearing and/or impeller.
• Check the bearings and the impeller for damage.
• Replace the bearings or the impeller, if necessary.
Electrical defects.
• Check that the voltage and frequency of the power
supply are correct.
• Remedy the possible defects in the motor.
• Check that the motor is properly cooled.
The speed is too high.
• Check that the frequency of the power supply
corresponds to the frequency stated on the motor
nameplate.
8.7 Vibrations
Cause Remedy
The shaft is bent due to damage.
• Check the deflection of the shaft. The total indicator
runout must not exceed 0.05 mm.
• Possibly replace the shaft.
Mechanical failure of bearing and/or impeller.
• Check the bearings and the impeller for damage.
• Replace the bearings or the impeller, if necessary.
Misalignment.
• Realign the pump and the motor.
The foundation is not rigid enough.
41
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