Your boiler has detected an electrical fault or a sensor failure and has shut down as a safety precaution.

Electronics/NTC fault | Short-circuit in flow or return NTC or electronics defective

What causes this fault?

This fault occurs when the boiler's control system receives nonsensical temperature readings, such as an impossible jump in heat or a signal suggesting a short circuit. The most common reason is that one of the internal temperature sensors has failed electrically or the main control board is no longer able to process data correctly. Because the boiler cannot accurately monitor how hot the water is, it shuts down to prevent overheating and internal damage.