Emergency
F3 on Viessmann Vitodens 100-W WB1C 30kW Combi Boiler

The boiler has detected a flame when it should not be lit, so it has stopped as a safety precaution and will need a qualified engineer to check it before it is used again.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Flame signal is already present at burner start

From this model's manual
Verified against the Viessmann/Viessmann Vitodens 100 W Wb1c 5609059 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

F4View →F5View →

All 26 fault codes on the Vitodens 100-W WB1C 30kW Combi Boiler

Seeing a different code? Every code this model can display, in one place.

5A101830385051525859A9b0b8E3E5F0F1F2F4F8F9FAFCFdFF

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