Fault Finding; Pump Set With Electric Motor - Grundfos Fire NKF Montage- Und Betriebsanleitung

16. Fault finding

16.1 Pump set with electric motor

Warning
Before removing the terminal box cover of the
motor, opening the control cabinet or before
starting service work, switch off the power
supply. Make sure that the power supply cannot
be accidentally switched on.
Fault Cause
1. Pump delivers no a) Wrong electrical connection.
or too little water.
b) Wrong direction of rotation.
c) Air in suction pipe.
d) Counter-pressure too high.
e) Inlet pressure too low.
f) Suction pipe or impeller blocked by impurities.
g) Pump draws in air due to defective seals.
2. Motor is a) Pump blocked by impurities.
overloaded.
b) Pump running above the rated duty point.
c) Motor-protective circuit breaker is not set up
correctly.
d) Motor runs on two phases.
3. Pump makes too a) Inlet pressure too low (cavitation).
much noise.
Pump runs
unevenly and
b) Air in suction pipe or pump.
vibrates.
c) Counterpressure is lower than specified.
d) Impeller out of balance
(clogged impeller blades).
e) Inner parts are worn.
f) Pump stressed by the pipework
(causing starting noise).
g) Defective bearings.
h) Defective motor fan.
i) Defective coupling.
j) Foreign bodies in the pump.
4. Leaking pump a) Pump is stressed by the pipework (causing
housing, shaft seal leaks from the pump body or the connections.
or connections.
b) Pump housing seals or gasket at connections
are defective.
c) Shaft seal is dirty or seized up.
d) Shaft seal is defective.
e) Shaft surface or shaft sleeve is defective.
5. Too high pump or a) Air in the suction pipe or pump.
motor temperature.
b) Inlet pressure is too low.
c) Bearings lubricated with too little, too much or
unsuitable lubricant.
d) Pump bearing bracket stressed by the
pipework.
e) Axial thrust too high.
f) Motor-protective circuit breaker is defective or
not set correctly.
g) Motor is overloaded.
All manuals and user guides at all-guides.com
Remedy
Check the electrical installation.
Interchange two phases of the power supply.
Vent and fill the suction pipe and pump.
Set the duty point in accordance with the data sheet.
Check the system for impurities.
Make sure that all the conditions described in section
9.2 Minimum inlet pressure and 10.6 Pipe connection
are complied with.
Clean the suction pipe or pump.
Check the pipeline seals, pump housing gaskets and
shaft seals, and replace, if necessary.
Clean the pump.
Set the duty point in accordance with the data sheet.
Check the setting of the motor-protective circuit breaker
and replace, if necessary.
Check the electrical connection. Replace the fuse, if
defective.
Ensure that the conditions described in section
9.2 Minimum inlet pressure and 10.6 Pipe connection
have been met.
Vent and fill the suction pipe or pump.
Set the duty point in accordance with the data sheet.
Clean and check the impeller.
Replace defective parts.
Mount the pump so that it is not stressed.
Support the pipes.
Replace the bearings.
Replace the fan.
Replace the coupling.
Clean the pump.
Mount the pump so that it is not stressed.
Support the pipes.
Replace housing seals or connection seals.
Clean and check the shaft seal.
Replace the shaft seal.
Replace the shaft or shaft sleeve.
Vent and fill the suction pipe or pump.
Ensure that the conditions described in section
9.2 Minimum inlet pressure and 10.6 Pipe connection
have been met.
Add or reduce the amount of or replace the lubricant.
Mount the pump so that it is not stressed. Support the
pipes. Check the alignment of the coupling. See section
10.5 Alignment.
Check relief bores on the impeller and gap rings on the
inlet.
Check the settings for the motor-protective circuit
breaker, replace if necessary.
Reduce flow rate.
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