Measurement:

Select appropriate fault code:
F.0 FLOW NTC
F.1 RETURN NTC
F.3 DHW SENSOR
F.10 FLOW NTC
F.11 RETURN NTC
F.13 DHW SENSOR
F.20 OVERHEAT CUT OFF
F.22 TEMPERATURE DIFFERENTIAL EXCESSIVE
F.23 TEMPERATURE DIFFERENTIAL EXCESSIVE
F.24 TEMPERATURE DIFFERENTIAL EXCESSIVE
F.25 LOW WATER PRESSURE
F.27 NO DEMAND TO GAS VALVE
F.28 IGNITION LOCKOUT