What does the Viessmann Vitodens 050-W E321 fault code mean?
The E321 fault code indicates a problem with the system venturi, which is responsible for mixing air and gas for combustion. This issue can lead to inefficient operation or complete shutdown of the boiler.
Common Causes
- Blocked Venturi: Debris or blockages can prevent proper airflow, affecting combustion efficiency.
- Faulty Pressure Sensor: A malfunctioning pressure sensor may incorrectly report conditions, leading to the E321 fault code.
Can I fix it myself? (DIY)
It is strongly advised to call a Gas Safe Engineer for this issue, as it involves gas and combustion components that require professional handling for safety and compliance.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the E321 fault code is around £150 to £250. This includes potential cleaning or replacement of the venturi and associated components, which can be labour-intensive.