E1 224
Worcester Bosch Flame Detection Error at Start-Up

Boiler displays E1 224, often immediately after start-up, with no sustained flame.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Incorrect polarity or poor earth connection, Faulty flame sensing electrode, Moisture on PCB or electrode connections, Control PCB fault

How to Fix / Troubleshooting

Safety first: Isolate the boiler from the mains before inspecting wiring. Only competent persons should remove the case.

  • Check mains polarity: Ensure live, neutral, and earth are correctly connected at the boiler's terminal block. Incorrect polarity can prevent flame detection.
  • Inspect earth connection: Verify that the earth wire is securely connected to the boiler chassis and terminal.
  • Check for moisture: Look for signs of water ingress around the PCB and wiring harness. If present, identify and repair the source of the leak (e.g., auto air vent, pump union) and dry/replace affected components.
  • Engineer checks: A technician should test the ionisation electrode, wiring harness, and PCB, and confirm correct microamp flame signal during operation.
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Repair Difficulty

Hard 4/5

Required Part

Main Control PCB
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