What does the Viessmann Vitodens 100-W F23 fault code mean?
The F23 fault code on the Viessmann Vitodens 100-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
- Gas Supply Issues: Insufficient gas supply or a blockage in the gas line can prevent the burner from igniting.
- Flame Sensor Problems: A faulty or dirty flame sensor may fail to detect the flame, causing the boiler to shut down.
Can I fix it myself? (DIY)
It is advisable to call a Gas Safe Engineer for any gas or electrical issues, as working on these systems can be dangerous. However, you can check the gas supply and ensure the boiler is properly reset according to the manufacturer’s instructions.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for resolving the F23 fault could range from £150 to £300, depending on whether the issue is a simple gas supply blockage or requires replacement of the flame sensor, which typically costs around £100 to £200.