BoilerFaultCodesTechnical description
Circulation Fault (Primary Circuit). Displayed if: i) Within 15 seconds of burner lighting water temperature hasn't changed by 1 degree. ii) Within 10 minutes of burner lighting water temperature twice exceeds selected temperature by 30 degrees.
What causes this fault?
This fault occurs when the boiler detects that water is not moving around the internal system fast enough to carry heat away from the burner. The most common reasons are a seized internal pump that has failed to start or a build-up of sludge and debris blocking the narrow pipes within the main heat exchanger. When the water stays still, it overheats almost instantly, triggering a safety shutdown to prevent damage.
This issue often surfaces at the start of autumn when the heating is turned on for the first time after summer, as the pump can 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.