E9 224
Worcester Bosch
Intermittent Overheat / Flame Loss Combination Fault
Boiler intermittently locks out with E9 224, often during high demand.
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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
Partially blocked primary heat exchanger, Pump running at incorrect speed, Incorrect gas rate causing overheating, Faulty temperature sensor
How to Fix / Troubleshooting
Safety first: Do not continue resetting a boiler that repeatedly overheats. Allow it to cool and isolate power.
- Check all radiators are open: Ensure TRVs and lockshields are open enough to allow adequate flow.
- Bleed system: Remove air from radiators and high points, then top up pressure.
- Observe boiler operation: If the temperature on the display rises very quickly to maximum before lockout, circulation or heat exchanger fouling is likely.
- Engineer tasks: A Gas Safe engineer should check pump speed settings, flush the system, inspect the primary heat exchanger, and verify combustion and gas rate.
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Repair Difficulty
Professional Required
5/5
Required Part
Circulation Pump
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