Fault Finding - Grundfos NB Serie Instrucciones De Instalación Y Funcionamiento

16. Fault finding

Warning
Before removing the terminal box cover
and before removing/dismantling the
pump, make sure that the power supply
has been switched off and that it cannot be
accidentally switched on again.
Fault Cause
1. Pump delivers a)
no or too little
liquid.
b)
c)
d)
e)
f)
g)
h)
2. Motor- a)
protective
b)
circuit breaker
has tripped
because the c)
motor is
overloaded.
d)
e)
Wrong electrical connection, for
instance two phases.
Wrong direction of rotation.
Air in inlet pipe.
Counter-pressure is too high.
Inlet pressure is too low.
Inlet pipe or impeller blocked by
impurities.
Pump draws in air due to defective
seal.
Pump draws in air due to low liquid
level.
Pump blocked by impurities.
Pump running above rated duty
point.
Density or viscosity of liquid higher
than specified when ordering.
Motor-protective circuit breaker
overload setting incorrect.
Motor runs on two phases.
Remedy
Check the electrical connection and remedy,
if necessary.
Interchange two phases of the power supply.
Vent the inlet pipe or the pump.
Set the duty point in accordance with the
data sheet. Check the system for impurities.
Increase the liquid level on the inlet side.
Open the isolating valve in the inlet pipe.
Make sure that all the conditions in section
8.5 Pipework are complied with.
Clean the inlet pipe or pump.
Check the pipeline seals, pump housing
gaskets and shaft seals. Replace gaskets
and seals, if necessary.
Increase the liquid level on the inlet side and
keep it as constant as possible.
Clean the pump.
Set the duty point in accordance with the
data sheet.
If less flow is sufficient, reduce the flow on
the outlet side. Otherwise, fit a more
powerful motor.
Check the setting of the motor-protective
circuit breaker and adjust it, if necessary.
Check the electrical connection. Replace the
fuse, if defective.
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