Grundfos CM 1, Service Instructions Manual

Page: 15 / 24

English (GB)
15
6. Fault finding
Warning
Before removing the terminal box cover, make sure that the electricity supply has been switched off.
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
1. The pump does not run. a) Supply failure. Switch on the switch.
Check cables and cable connections for
defects and loose connections.
b) Fuses are blown. Check cables and cable connections for
defects, and replace the fuses.
c) Motor protection tripped. See 2. a), b), c), d), e), f).
d) Control-current circuit defective. Repair or replace the control-current circuit.
2. Motor-protective circuit breaker has
tripped (trips out immediately when
supply is switched on).
a) Fuses are blown. See 1. b).
b) Contacts of the motor-protective circuit
breaker or magnet coil defective.
Replace the contacts of the motor-protective
circuit breaker, the magnet coil or the entire
motor-protective circuit breaker.
c) Cable connection is loose or faulty. Check cables and cable connections for
defects, and replace the fuses.
d) Motor winding is defective. Repair or replace the motor.
e) The pump is mechanically blocked. Switch off the electricity supply, and clean or
repair the pump.
f) The setting of the motor-protective
circuit breaker is too low. Set the motor-protective circuit breaker
according to the rated current of the motor
(I
1/1
). See nameplate.
3. The motor-protective circuit breaker
trips out occasionally.
a) The setting of the motor-protective
circuit breaker is too low.
See 2. f).
b) Periodic supply failure. See 2. c).
c) Periodically low voltage. Check cables and cable connections for
defects and loose connections.
Check that the supply cable of the pump is
correctly sized.
4. The motor-protective circuit breaker
has not tripped out, but the pump is
inadvertently out of operation.
a) See 1. a), b), d) and 2. e).
5. The pump performance is unstable. a) Pump inlet pressure too low. Check the inlet conditions of the pump.
b) Inlet pipe is partly blocked by impurities. Remove and clean the inlet pipe.
c) Leakage in inlet pipe.
Remove and repair the inlet pipe.
d) Air in inlet pipe or pump. Vent the inlet pipe/pump.
Check the inlet conditions of the pump.
6. The pump runs, but gives no water. a) Pump inlet pressure too low. See 5. a).
b) Inlet pipe partly blocked by impurities. See 5. b).
c) The foot or non-return valve is stuck in
its closed position.
Remove and clean, repair or replace the valve.
d) Leakage in inlet pipe. See 5. c).
e) Air in inlet pipe or pump. See 5. d).
7. The pump runs backwards when
switched off.
a) Leakage in inlet pipe. See 5. c).
b) Foot or non-return valve defective. See 6. c).
c) The foot valve is stuck in completely or
partly open position.
See 6. c).
8. The pump runs with reduced
performance.
a) 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.
b) See 5. a), b), c), d).