What does the Viessmann Vitodens 111-W F91 fault code mean?
The F91 fault code indicates a faulty heating circuit configuration in the Viessmann Vitodens 111-W boiler. This typically means there is an issue with the setup or communication within the heating system that prevents it from operating correctly.
Common Causes
- Incorrect Wiring: Misconfigured or damaged wiring can disrupt the communication between components in the heating circuit.
- Faulty Sensors: Malfunctioning temperature or pressure sensors may provide incorrect readings, leading to a misconfiguration error.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as it involves complex electrical and gas components that require professional expertise to ensure safety and compliance with regulations.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F91 fault code is around £150 to £250. This includes diagnostics and potential replacement of faulty sensors or wiring, which are common issues associated with this fault.