BoilerFaultCodesWorcester Bosch 8/2/1 Fault Code
Also written as 821 — same fault.
The Worcester Bosch 8/2/1 fault code means: your boiler is currently struggling to communicate with your wall-mounted heating controller, meaning it hasn't been set up correctly to read your home's temperature.. It appears on 1 Worcester Bosch model in our database.
Technical description: RC35-HK1 remote control. No remote control assigned, although room temperature control has been set.
DIY fix possible
Check that the thermostat or remote controller is powered on and has fresh batteries if applicable.Ensure the controller is securely clicked into its wall bracket to establish a solid connection.Navigate to the controller settings menu to re-pair or re-assign the unit to the boiler according to the installation manual.
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Worcester Bosch models that show the 8/2/1 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Worcester Bosch 8/2/1 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026