BoilerFaultCodesTechnical description
The overheat thermostat has operated and requires manual re-setting. An overheat condition has occurred.
What causes this fault?
This fault occurs when the water inside the heat exchanger reaches a dangerously high temperature, triggering a safety switch to cut the power. The most common reasons are a failed pump that isn't moving water away from the boiler quickly enough or a blockage in the system pipework. It can also happen if the internal sensors fail and wrongly report that the boiler is boiling over.
This fault is more common when the heating is first turned on after summer, as circulating pumps often seize up 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.