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13. Fault finding chart
13.1 Megging
Megging of DP and EF pumps is not allowed, as the
built-in electronics may be damaged.
Warning
Before attempting to diagnose any fault, make sure that the fuses have been removed or the
mains switch has been switched off. It must be ensured that the power supply cannot be
accidentally switched on.
All rotating parts must have stopped moving.
Warning
All regulations applying to pumps installed in potentially explosive environments must be
observed.
It must be ensured that no work is carried out in potentially explosive atmosphere.
Fault
Cause
Remedy
1. The pump does not run.
a) The dry-running sensors are not
covered by liquid.
After power-on:
Allow the liquid level
to rise until the dry-running sensors
are covered with liquid.
b)
Three-phase pumps only:
The pump is connected to the
power supply with a wrong phase
sequence.
Interchange L1 and L2.
c) Fuses in electric installation
blown.
Replace blown fuses. If the new ones
blow too, check the electric
installation and the submersible drop
cable.
d) Supply failure; short-circuit; fault
in cable or motor winding.
Have the cable and motor checked
and repaired by a qualified
electrician.
e) Fault in motor electronics.
Have the motor checked and repaired
by a Grundfos service engineer.
f)
Deposits on level or dry-running
sensors.
Clean the sensor(s).
2. The pump operates, but
the motor stops after a
short while.
a) Impeller blocked by impurities.
Increased current consumption in
all three phases.
Clean the impeller.
b) Increased current consumption
due to large voltage drop.
Check that the supply voltage is
within the range.
c) Too high liquid temperature.
Reduce the liquid temperature.
d) Too high liquid viscosity.
Dilute the liquid.
3. The pump operates at
below-standard
performance and power
consumption.
a) Discharge pipe partly blocked by
impurities.
Clean the discharge port.
b) Valves in the discharge pipe
partly closed or blocked.
Check and clean or replace the
valves, if necessary.
4. The pump operates, but
delivers no liquid.
a) Discharge valve closed or
blocked.
Check the discharge valve, and
possibly open and/or clean it.
b) Non-return valve blocked.
Clean the non-return valve.
Vent the pump.
c) Air in pump.
