BoilerFaultCodesTechnical description
Temperature too high during domestic hot water (DHW) demand
What causes this fault?
This fault occurs when the water meant for your taps becomes dangerously overheated, triggering a safety shutdown to prevent scalding. The most common reason is that the boiler's internal sensors are giving incorrect readings, or the flow of water through the heat exchanger is being restricted by limescale or a mechanical failure. In some cases, a faulty valve may be sending heat to the wrong place, causing the temperature to spike rapidly.
This fault is often more noticeable in summer when the incoming mains water is naturally warmer, making it easier for the boiler to exceed its maximum safety temperature.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.