What does the Viessmann Vitodens 111-W F23 fault code mean?
The F23 fault code on the Viessmann Vitodens 111-W indicates a flame failure, meaning the boiler is unable to detect a flame during operation. This can lead to the boiler shutting down to prevent unsafe conditions.
Common Causes
- Insufficient Gas Supply: A blockage or issue in the gas supply line can prevent the boiler from receiving the necessary gas to ignite.
- Faulty Flame Sensor: If the flame sensor is dirty or malfunctioning, it may not detect the flame, causing the boiler to shut down.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for any gas or electrical issues, as these can be dangerous. However, you can check the gas supply and ensure that the boiler is properly reset according to the manufacturer’s instructions.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for a faulty flame sensor is around £150, including parts and labour. This is based on the typical cost of a replacement sensor and the time required for a qualified engineer to perform the repair.