How to fix Baxi 600 Series fault code E720

What does the Baxi 600 Series E720 fault code mean?

The E720 fault code on the Baxi 600 Series indicates a flame failure during the domestic hot water (DHW) operation. This means the boiler is unable to detect a flame when it attempts to heat water, which can lead to a lack of hot water supply.

Common Causes

  • Blocked Flue: A blockage in the flue can prevent proper ventilation, causing the boiler to shut down due to safety mechanisms.
  • Faulty Flame Sensor: If the flame sensor is dirty or malfunctioning, it may not detect the flame, leading to a shutdown.

Can I fix it myself? (DIY)

While some issues may be resolved by checking and clearing any blockages in the flue, it is crucial to call a Gas Safe Engineer for any gas or electrical-related problems to ensure safety and compliance with regulations.

Estimated Repair Cost (2026 UK Prices)

The estimated repair cost for addressing the E720 fault could range from £100 to £250, depending on whether the issue is a simple flue blockage or requires replacement of the flame sensor, which typically costs around £150.