Boiler shows E1 227 (or 227) and locks out, indicating flame loss during operation.

Safety first: Switch off power and close the gas isolation valve if you smell gas. Do not attempt to adjust gas components yourself.

• Check other gas appliances: Confirm whether cookers or other boilers are operating normally. If all appliances are affected, contact your gas supplier.
• Inspect flue and air intake: Ensure the Worcester Bosch flue terminal is clear and correctly fitted. A blocked flue can cause poor combustion and flame loss.
• Condensate drain check: Make sure the condensate trap and pipe are not blocked. A gurgling sound or water backing up can extinguish the flame.
• Reset once: After basic checks, press the reset button. If the fault recurs, do not repeatedly reset.
• Engineer actions: A qualified engineer should inspect and clean the burner, check the ionisation electrode and cable, verify gas valve operation and modulation, and measure combustion using a flue gas analyser to ensure correct CO₂/O₂ levels.