What does the Baxi Megaflo E420 fault code mean?
The E420 fault code on a Baxi Megaflo indicates a central heating (CH) flow rate fault, which suggests that the flow of water through the heating system is either too low or not functioning correctly. This can lead to inadequate heating performance and may require immediate attention to avoid further issues.
Common Causes
- Blocked Pipes: Debris or sludge buildup in the heating system can restrict water flow, causing the E420 fault.
- Faulty Pump: A malfunctioning circulation pump may fail to move water effectively, leading to low flow rates.
Can I fix it myself? (DIY)
If you are experienced with heating systems, you can check for blockages in the pipes and ensure the pump is operational. However, if you are unsure or if gas/electrical components are involved, it is strongly advised to call a Gas Safe Engineer for safety reasons.
Estimated Repair Cost (2026 UK Prices)
The estimated repair cost for addressing the E420 fault could range from £150 to £300, depending on whether the issue is a simple blockage or requires pump replacement. A new pump typically costs around £200, plus labour.