BoilerFaultCodesTechnical description
Safety temperature limiter has tripped – top-up water until the reset pressure is reached
What causes this fault?
This fault occurs when the internal safety sensor detects that the heat exchanger has become dangerously hot, causing the boiler to shut down to prevent damage. The most common reason is a lack of water circulating through the system, often due to low pressure, a blockage, or a pump failure. If there isn't enough water to carry the heat away to your radiators, the temperature inside the unit rises too quickly.
This issue often surfaces when the heating is first turned on in autumn, as pump components can seize or air locks can develop after being idle during the summer.
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.