Grundfos CM series, Service Instructions Manual

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6.4 The motor-protective circuit breaker has not tripped out, but the pump is inadvertently out of operation.
Cause Remedy
Supply failure. • Switch on the switch.
• Check cables and cable connections for defects and loose
connections.
Fuses are blown. • Check cables and cable connections for defects, and replace the
fuses.
Control-current circuit defective. • Repair or replace the control-current circuit.
The pump is mechanically blocked. • Switch off the electricity supply, and clean or repair the pump.
6.5 The pump performance is unstable.
Cause Remedy
Pump inlet pressure too low. • Check the inlet conditions of the pump.
Inlet pipe is partly blocked by impurities. • Remove and clean the inlet pipe.
Leakage in inlet pipe. • Remove and repair the inlet pipe.
Air in inlet pipe or pump. • Vent the inlet pipe/pump.
• Check the inlet conditions of the pump.
6.6 The pump runs, but gives no water.
Cause Remedy
Pump inlet pressure too low. • Check the inlet conditions of the pump.
Inlet pipe partly blocked by impurities. • Remove and clean the inlet pipe.
The foot or non-return valve is stuck in its closed position. • Remove and clean, repair or replace the valve.
Leakage in inlet pipe. • Remove and repair the inlet pipe.
Air in inlet pipe or pump. • Vent the inlet pipe/pump.
• Check the inlet conditions of the pump.
6.7 The pump runs backwards when switched off.
Cause Remedy
Leakage in inlet pipe. • Remove and repair the inlet pipe.
Foot or non-return valve defective. • Remove and clean, repair or replace the valve.
The foot valve is stuck in completely or partly open position. • Remove and clean, repair or replace the valve.
6.8 The pump runs with reduced performance.
Cause Remedy
Wrong direction of rotation. • Three-phase pumps only:
Switch off the electricity supply with the external circuit breaker and
interchange two phases in the pump terminal box.
It is possible to check the direction of rotation by means of the
installation indicator.
Black: The direction of rotation is correct.
White: The direction of rotation is incorrect.
Pump inlet pressure too low. • Check the inlet conditions of the pump.
Inlet pipe is partly blocked by impurities. • Remove and clean the inlet pipe.
Leakage in inlet pipe. • Remove and repair the inlet pipe.
Air in inlet pipe or pump. • Vent the inlet pipe/pump.
• Check the inlet conditions of the pump.
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English (GB)