What does the Viessmann Vitodens 100-W F26 fault code mean?
The F26 fault code on the Viessmann Vitodens 100-W indicates a malfunction with the flow sensor, which is responsible for monitoring the flow of water through the heating system. This issue can lead to improper heating performance and may prevent the boiler from operating efficiently.
Common Causes
- Faulty Flow Sensor: The flow sensor may be defective or damaged, leading to incorrect readings and triggering the fault code.
- Blocked or Dirty Sensor: Accumulation of debris or limescale on the sensor can impede its function, causing it to fail to detect water flow accurately.
Can I fix it myself? (DIY)
It is recommended to call a Gas Safe Engineer for this issue, as working with gas appliances can be dangerous. Attempting to fix the flow sensor without proper training may lead to further complications or safety hazards.
Estimated Repair Cost (2026 UK Prices)
The estimated cost for repairing or replacing the flow sensor on a Viessmann Vitodens 100-W is around £150 to £250. This includes the cost of the part and labour, as flow sensors are typically priced between £50 and £100, with additional charges for professional installation.