BoilerFaultCodesVokera E21 Fault Code
The Vokera E21 fault code means: your boiler has shut itself down for safety because a critical fault has been detected that requires a manual reset.. It appears on 2 Vokera models in our database.
Technical description: The safety devices have been activated (lockout)
What causes the Vokera E21 fault?
This fault occurs when the boiler's safety sensors detect a failure in the ignition process or a consistent loss of flame during operation. The system shuts down to prevent unburnt gas from building up, often triggered by a worn-out ignition spark, a faulty gas supply, or a communication error within the internal electronics.
This fault can be more frequent during the first cold snap of winter when components that have sat idle all summer are suddenly put under high operational stress.
DIY fix possible
Locate the reset button or selector switch on the control panelTurn the selector to the 'RESET' position for 5-10 secondsRelease the switch and wait for the boiler to attempt to restart; if the code returns or happens frequently, call an engineer
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Gas Safe Register →Vokera models that show the E21 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera E21 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026