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Code Faults
Cause
of the
fault
Description
Checking / solution
L11
RET-DEP>MAX
PCU
Difference between the flow
and return temperatures too
great
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
Maximum boiler temperature
exceeded (STB thermostat
maximum)
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
Sensor fault
4
Replace the STB if necessary
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
L14
BURNER FAILURE
PCU
5 burner start-up failures
No ignition
4
Check the wiring between the PCU PCB and the
ignition transformer
4
Check that the SU PCB is correctly in place
4
Check the ionization/ignition electrode
4
Check the earthing
4
SU PCB faulty: Change the PCB
Ignition arc, but no flame formation
4
Vent the gas flues
4
Check that the gas valve is fully opened
4
Checking the gas supply pressure
4
Check the operation and setting of the gas valve
unit
4
Check that the air inlet and flue gas discharge flues
are not blocked
4
Check the wiring on the gas valve unit
4
SU PCB faulty: Change the PCB
Presence of the flame but insufficient ionization (<3 µA)
4
Check that the gas valve is fully opened
4
Checking the gas supply pressure
4
Check the ionization/ignition electrode
4
Check the earthing
4
Check the wiring on the ionization/ignition
electrode
MCA 25/28 BIC
8. Troubleshooting
15/06/12 - 300022159-001-01
101
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