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15
9. Fault finding
This section consists of two subsections, i.e. for pumps with terminal box with standard module and for twin-
head pumps with terminal box with relay module.
9.1 Single-head and twin-head pumps with standard module
Warning
Before removing the terminal box cover, make sure that the power supply has been switched
off and that it cannot be accidentally switched on.
The pumped liquid may be scalding hot and under high pressure.
Before any removal or dismantling of the pump, the system must therefore be drained, or the
isolating valves on either side of the pump must be closed.
Fault Cause Remedy
The pump does not run.
None of the indicator
lights are on.
One fuse in the installation is
blown.
Replace the fuse.
External mains switch switched
off.
Switch on the mains switch.
Current-/voltage-operated earth-
leakage circuit breaker has
tripped out.
Repair insulation defects, and cut in the circuit
breaker.
The pump has been cut out by
the thermal overload switch.
Check that the liquid temperature falls within
the specified range.
With external on/off changeover contact:
The pump will restart automatically when it has
cooled to normal temperature.
With external on/off impulse contacts:
The pump can be restarted when it has cooled
to normal temperature.
The pump does not run.
The green indicator light
is on.
Rotor blocked, but the pump has
not been cut out by the thermal
overload switch.
Switch off the power supply, and clean or
repair the pump.
The speed switch module has
not been fitted.
Switch off the power supply with the external
mains switch, and fit the speed switch module.
Only three-phase
pumps:
The pump is running.
The red and green
indicator lights are on.
The pump is running with wrong
direction of rotation.
Switch off the power supply with the external
mains switch, and interchange two phases in
the pump terminal box.
Noise in the system.
The green indicator light
is on.
Air in the system. Vent the system.
The flow is too high.
Reduce the pump performance
(change to lower speed).
The pressure is too high.
Reduce the pump performance
(change to lower speed).
Noise in the pump.
The green indicator light
is on.
Air in the pump. Vent the pump.
The inlet pressure is too low.
Increase the inlet pressure, and/or check the
air volume in the expansion tank, if installed.
Insufficient heat in some
places in the heating
system.
The pump performance is too
low.
Increase the pump performance
(change to higher speed),
if possible, or replace the pump with a pump
with a higher flow.
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