Technical data

24
FAULT FINDING
Before fault finding, make sure that:
- All gas cocks are open and there is an inlet gas pressure of 20 mbar (G 20).
- The heating system pressure is at least 1 bar.
- There is a permanent mains supply to the boiler.
- The fuses on the PCB are intact.
- All external controls are correctly wired and calling for heat.
WARNING: Always isolate the boiler from the electrical supply before carrying out any electrical replace-
ment work. Always check for gas soundness after any service work.
Digital display shows:
- CH temperature (no decimal point displayed)
- DHW temperature (decimal point displayed)
- diagnostic error messages
- pressure in CH system
- boiler output setting
As soon as the mains switch is on the display shows for a very short time the version of software used. It
has no importance for boiler operation.
Diagnostic error messages
In the event of a fault the following diagnostic error messages will be displayed:
Message Fault Action Comments
F0 Loss of system water Refill system Pump runs for one
Check for leaks minute
Boiler is restarted by
switching of main
switch
Air lock in boiler Bleed boiler and system
Pressure sensor failure Check the pressure sensor
(Sensing inlet must not be clogged)
F1 No flame detected Check flame sense electrode
and connecting cable
Check ignition electrode
Check ignition unit on gas valve
Check fan operation
Overheating of the boiler Reset overheat thermostats If overheat thermo-
Check the pump revolution stats are blocked,
boiler does not ignite
when starting
F2 Central heating thermistor Check if flow thermistor is not
failure disconnected or short-circuited
Sensor Ohm resistance
10 kΩ by 25°C, 12,7 kΩ by 20°C,
16 kΩ by 15°C
CH water temperature Check if system is not frozen
below 3°C
F3 Heat exchanger blockage Check main heat exchanger Boiler shuts down and
Check domestic heat pump runs
exchanger
F4 Domestic hot water Check thermistor/leads Domestic hot water is
thermistor faulty Sensor Ohm resistance: available bur poor
10 kΩ by 25°C
12,7 kΩ by 20°C
16 kΩ by 15°C