What does the Baxi 600 Series E400 fault code mean?
The E400 fault code on the Baxi 600 Series indicates a “DHW dry fire” condition, which means that the boiler has detected that there is no water flow when attempting to heat domestic hot water. This can lead to overheating and potential damage if not addressed promptly.
Common Causes
- Low Water Pressure: Insufficient water pressure can prevent the boiler from detecting water flow, triggering the E400 fault code.
- Blocked or Faulty Diverter Valve: A malfunctioning diverter valve may not allow water to flow correctly to the hot water system, causing the boiler to register a dry fire condition.
Can I fix it myself? (DIY)
Before attempting any repairs, check the boiler’s pressure gauge and ensure it is within the recommended range (typically 1-1.5 bar). If the pressure is low, you can safely re-pressurise the system using the filling loop. However, for issues related to the diverter valve or any gas/electrical components, it is crucial to call a Gas Safe Engineer.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the E400 fault code could range from £150 to £300, depending on whether the issue is simply low water pressure or requires replacement of the diverter valve, which can be more expensive due to parts and labour.