User Manual

Code Faults Cause
of the
fault
Description Checking / solution
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<MIN
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 DEP-RET>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
L14 BURNER FAILURE
PCU 5 burner start-up failures No ignition
4 Contact the professional who takes care of
maintenance of the appliance
Presence of the ignition arc but no flame formation
4 Check that the gas valve is fully opened
4 Contact the professional who takes care of
maintenance of the appliance
Presence of the flame but insufficient ionization
(<3 µA)
4 Check that the gas valve is fully opened
4 Contact the professional who takes care of
maintenance of the appliance
6. Troubleshooting MCA 15 - MCA 25 MCA 25/28 MI
35
23/08/2011 - 300024159-001-B