Code Faults Cause
of the
fault
Description Checking / solution
L11 DEF.DT.RET.ECH
PCU Difference between the return
temperature and the exchanger
temperature too big
Sensor fault
4 Check the Ohmic value of the sensor
4 Replace the sensor if necessary
Bad connection
4 Check that the sensor has been correctly fitted
No water circulation
4 Vent the air in the heating system
4 Check the circulation (direction, pump, valves)
4 Check the water pressure
4 Check the cleanliness of the heat exchanger
4 Check that the heating pump is operating
correctly
L12 STB OPEN
PCU
4 Maximum boiler temperature
exceeded (STB thermostat
maximum)
4 Air differential pressure switch
has been triggered
Bad connection
4 Check the wiring between the PCU PCB and the
STB
4 Check that the SU PCB is correctly in place
4 Check the electrical continuity of the STB
4 Check whether the STB has been correctly fitted
STB failure
4 Replace the STB if necessary
4 Check that the sensor has been correctly fitted
4 Check for correct operation
No water circulation
4 Remove the air from the installation
4 Check the circulation (direction, pump, valves)
4 Check the water pressure
4 Check the cleanliness of the heat exchanger
4 Check that the heating pump is operating
correctly
Air pressure switch is triggered
4 Check that the air inlet and flue gas discharge
flues are not blocked
4 Check that condensate has been removed and
the cleanliness of the siphon
4 Check the cleanliness of the heat exchanger
(Flue gas dimensions)
Diematic iSystem For C 330 / C 630 ECO 7. Troubleshooting
31082018 - 7600691-001-06
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