Your boiler is struggling to move water around the system properly, which is causing it to shut down to prevent overheating.

Primary circuit error circulation fault

What causes this fault?

This fault occurs when the boiler detects that water is not moving through the internal pipes quickly enough to take the heat away from the burner. The most common reasons are a failed pump that can no longer push the water, or a blockage caused by a build-up of sludge and debris in the system. Because the heat cannot escape, the boiler shuts down as a safety precaution to prevent the internal components from melting or cracking.