BoilerFaultCodesVokera E 12 Fault Code
Also written as E12 — same fault.
The Vokera E 12 fault code means: your boiler has detected that the water temperature in your underfloor heating circuit is outside of the expected safe range, causing the system to stop working.. It appears on 1 Vokera model in our database.
Technical description: Under-floor system temperature fault
What causes the Vokera E 12 fault?
This fault occurs when the water temperature entering your underfloor heating loops exceeds a safe threshold, triggered by a safety thermostat. The most common reasons are a failure in the external mixing valve that regulates heat or a pump failure that prevents hot water from moving through the system quickly enough. It is designed to prevent excessive heat from warping floorboards or damaging sensitive pipework.
This fault is more common in autumn and winter when the underfloor heating is first switched on after a long period of inactivity, which can lead to seized pumps or stuck valves.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Vokera models that show the E 12 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera E 12 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