Fault Finding - Grundfos CMB Instrucciones De Instalación Y Funcionamiento

7. Fault finding

Warning
Before starting work on the pump, make
sure that the power supply has been
switched off and that it cannot be
accidentally switched on.
Fault
1. The green light field
for "0 bar" is off even
if the power supply
has been switched
on.
2. The green "Pump
on" indicator light is
on, but the pump
does not start.
3. The pump does not
start when water is
consumed.
The "Pump on"
indicator light is off.
4. System without
pressure tank:
Frequent
starts/stops.
5. System with
pressure tank:
Frequent
starts/stops.
6. The pump does not
stop.
7. The red "Alarm"
indicator light is
permanently on.
Cause
a) The fuses in the electrical
installation have burnt.
b) The earth leakage circuit breaker
or the voltage-operated circuit
breaker has tripped.
c) No power supply.
d) The PM unit is defective.
a) The power supply to the pump is
disconnected after the PM unit.
b) The motor protection of the pump
has tripped due to overload.
c) The pump is defective.
d) The PM unit is defective.
a) Too big difference in height
between the PM unit and the
tapping point.
b) The PM unit is defective.
a) DIP switch 5 set to "ON".
b) Leakage in the pipework.
c) The non-return valve is stuck in
open position.
a) The pressure tank has no
precharge pressure, or the tank
size is insufficient.
b) Leaky non-return valve.
a) The pump cannot deliver the
necessary outlet pressure.
b) The start pressure is set too high.
c) The PM unit is defective.
d) The non-return valve is stuck in
open position.
a) Dry running. The pump needs
water.
b) The power supply to the pump is
disconnected after the PM unit.
c) The motor protection of the pump
has tripped due to overload.
d) The pump is defective.
e) The PM unit is defective.
Remedy
Replace the fuses. If the new fuses also
burn, check the electrical installation.
Cut in the circuit breaker.
Contact the power supply company.
Repair or replace the PM unit.
Check the plug and cable connections,
and check if the built-in circuit breaker of
the pump is switched off.
Check if the motor/pump is blocked.
Repair or replace the pump.
Repair or replace the PM unit.
Adjust the installation, or increase the
start pressure. See the quick guide.
Repair or replace the PM unit.
Set DIP switch 5 to "OFF". See the quick
guide.
Check and repair the pipework.
Clean or replace the non-return valve.
Check the tank precharge pressure, and
recharge the tank, if necessary.
If the size of the pressure tank is
insufficient, set DIP switch 5 to "OFF",
or replace the pressure tank.
Clean or replace the non-return valve.
Replace the pump.
Decrease the start pressure.
Repair or replace the PM unit.
Clean or replace the non-return valve.
Check the pipework.
Check the plug and cable connections,
and check if the built-in circuit breaker of
the pump is switched off.
Check if the motor/pump is blocked.
Repair or replace the pump.
Repair or replace the PM unit.
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