Worcester Bosch E9: Overheat lockout (E9 / 224)
Safety related: do not keep resettingWhat it means
The primary heat exchanger got too hot. Usually low water flow: pump fault, blockage, or air in the system.
Safe things to try first
- Check the pressure gauge reads 1 to 1.5 bar and top up if low.
- Bleed radiators.
When to call an engineer
If it returns after topping up, the pump, thermistor or heat exchanger needs checking.
Never remove the boiler cover or work on gas components yourself. It is illegal unless you are Gas Safe registered, and it will void your warranty.
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