BoilerFaultCodesVokera 20 Fault Code
The Vokera 20 fault code means: your boiler has detected a safety fault with the temperature sensors or internal wiring that prevents it from firing up.. It appears on 5 Vokera models in our database.
Technical description: Fault code 20 shows (from Fault Finding Test B)
What causes the Vokera 20 fault?
This fault occurs when the boiler's control board detects that the temperature sensors are sending an illogical signal or have disconnected entirely. It is usually caused by a physical failure of the internal thermistor or damage to the delicate wiring that connects these sensors to the main computer. Because the boiler can no longer accurately monitor how hot the water is, it shuts down as a safety precaution to prevent overheating.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Vokera models that show the 20 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera 20 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