BoilerFaultCodesViessmann F.15 Fault Code
Also written as F15 — same fault.
The Viessmann F.15 fault code means: your boiler has lost the ability to communicate with your solar heating system or auxiliary heat source, meaning you are relying solely on your main boiler for all hot water and heating.. It appears on 4 Viessmann models in our database.
Technical description: No solar DHW heating or central heating backup
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Viessmann models that show the F.15 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.15 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
- Viessmann Vitodens 100-W WB1A manual (PDF)
- Viessmann Vitodens 200-W B2HF System manual (PDF)
- Viessmann Vitodens 200-W B2KF Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026