Owner's manual

Code Faults Cause
of the
fault
Description Checking / solution
L07 BACK S.FAILURE
PCU The return temperature sensor is on
an open circuit
Bad connection
Sensor fault
4 Contact the professional who takes care of
maintenance of the appliance
L08 BACK S.FAILURE
PCU Return temperature too low Bad connection
Sensor fault
4 Contact the professional who takes care of
maintenance of the appliance
No water circulation
4 Vent the air in the heating system
4 Check the circulation (direction, pump,
valves)
4 Check the water pressure
L09 STB BACK
PCU Return temperature too high Bad connection
Sensor fault
4 Contact the professional who takes care of
maintenance of the appliance
No water circulation
4 Vent the air in the heating system
4 Check the circulation (direction, pump,
valves)
4 Check the water pressure
L10 DEP-RET>MAX
PCU Difference between the flow and
return temperatures insufficient
Bad connection
Sensor fault
4 Contact the professional who takes care of
maintenance of the appliance
No water circulation
4 Vent the air in the heating system
4 Check the circulation (direction, pump,
valves)
4 Check the water pressure
L11 RET-DEP>MAX
PCU Difference between the flow and
return temperatures too great
Bad connection
Sensor fault
4 Contact the professional who takes care of
maintenance of the appliance
No water circulation
4 Vent the air in the heating system
4 Check the circulation (direction, pump,
valves)
4 Check the water pressure
L12 STB OPEN
PCU Maximum boiler temperature
exceeded (STB thermostat
maximum)
Bad connection
Sensor fault
4 Contact the professional who takes care of
maintenance of the appliance
No water circulation
4 Vent the air in the heating system
4 Check the circulation (direction, pump,
valves)
4 Check the water pressure
MCA 15 - MCA 25 MCA 25/28 MI 6. Troubleshooting
15/06/12 - 300022161-001-01
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