BoilerFaultCodesVokera E091 Fault Code
The Vokera E091 fault code means: your boiler has detected that the main part responsible for heating your water is becoming blocked or dirty and needs a professional service.. It appears on 4 Vokera models in our database.
Technical description: Clean primary heat exchanger
What causes the Vokera E091 fault?
This fault occurs when the boiler detects a build-up of debris or mineral deposits inside the main heat exchanger, which restricts the flow of water. Over time, sludge from the central heating system or limescale from hard water coats the internal surfaces, making the boiler work harder and less efficiently. If left uncleaned, these deposits can prevent the heat from being transferred correctly, eventually leading to a full breakdown.
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 E091 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera E091 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