BoilerFaultCodesTechnical description
Overheat cut off device tripped. Thermostat, Overheat cut off device, Water differential pressure switch, or faulty Pump.
What causes this fault?
This fault occurs when the water inside the boiler exceeds a safe temperature, triggering a safety switch to shut the system down to prevent damage. The most common reasons are a pump failure preventing heat from leaving the boiler or a blockage in the system restricting water flow. It can also be caused by a faulty internal sensor that is incorrectly detecting a high temperature.
This issue often surfaces when the heating is first turned on after summer, as the internal pump can seize or get stuck during long periods of inactivity.
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.