Error E9 224

Safety precautions:

1) If the boiler is displaying E9 224, switch the boiler to the Off position and isolate from the mains if you need to work near it. Allow the boiler to cool before touching pipework or components. Do not remove the boiler casing or attempt gas or electrical repairs unless you are a qualified Gas Safe engineer. If you smell gas, evacuate the property and call the gas emergency number immediately.

Initial homeowner checks you can safely do:

1) Wait and reset: Allow the boiler to cool for 20–30 minutes, then press the reset button once according to the boiler manual. If the fault does not reappear and the system runs normally, observe it closely for a while to make sure it does not recur. Do not keep resetting repeatedly if the code returns.

2) Check condensate pipe: Inspect the condensate outlet/pipe (usually a small white plastic pipe running outside). In cold weather it can freeze. If frozen, carefully pour warm (not boiling) water over the external run to thaw it and clear any visible blockage. Check the internal condensate trap if you can access it without removing sealed panels (some models allow easy access); otherwise leave it for an engineer.

3) Check external flue: Look for obvious blockages at the flue terminal (birds’ nests, leaves, debris). Do not push objects into the flue; if anything is obstructing it, call an engineer.

4) Check visible leaks and pressure: Look at the boiler pressure gauge. If system pressure is significantly above the normal cold level (typical 1–1.5 bar depending on your system), reduce pressure by bleeding a radiator until the gauge returns to the normal range. If pressure is low, do not use the filling loop unless you are confident how to operate it — incorrect use can cause overpressure. If you see active leaks, isolate the boiler and call an engineer.

5) Listen for the pump: When the boiler attempts to run (after a reset), listen for the central heating pump. A noisy, intermittent or silent pump when it should be running can indicate a pump fault or seized impeller which will cause poor circulation and overheating. Do not open the pump casing; note the behaviour and report it to the engineer.

Specific diagnostic steps and fixes you can attempt or check before calling an engineer:

1) Single reset test: After cooling and completing the simple checks above, reset once. If the error does not return, monitor radiators and DHW for normal performance. If it returns immediately or shortly after, continue with the following.

2) Condensate and flue checks: If you confirmed the condensate was blocked and you cleared it and the fault cleared, that was likely the cause. If the external flue was obstructed and you cannot safely clear it, call an engineer.

3) Reduce system pressure safely by bleeding a radiator if overpressure is suspected. If you are unsure how to bleed a radiator, stop and call an engineer. Do not attempt to force open pressure relief devices.

4) Note any patterns: Does the fault appear only when the CH is on, only when hot water is demanded, or after a period of rapid firing? Provide these details to the engineer; they guide diagnosis (pump vs DHW heat exchanger vs flue thermostat).

When to call a professional / what the engineer will check:

1) Call a Gas Safe registered Worcester Bosch–accredited engineer if the error persists after the safe checks, if you find a seized pump, if there are signs of internal leakage, if the fan or flue assembly appears faulty, or if you are unable to access or clear condensate or flue obstructions. Do not attempt internal repairs or gas/electrical work yourself.

2) The engineer will perform safe diagnostic tests: check flue temperature sensors/thermostat, confirm pump operation and flow rates, inspect the fan and airflow, check for limescale or heat-exchanger blockages, test pressure relief valve function and system pressure, and scan the PCB for related faults. They will carry correct spares and follow manufacturer procedures.

Final notes:

1) Treat E9 224 seriously — it is a protective lockout for overheating. One-off faults after a reset that do not return may be benign, but repeated faults require professional attention. 2) Arrange an annual service with a Gas Safe engineer to reduce recurrence risk and to keep safety devices and sensors functioning correctly.