BoilerFaultCodesTechnical description
Water circulation fault
What causes this fault?
This fault occurs when the boiler detects a significant temperature difference between the water leaving the unit and the water returning to it, indicating that heat is not being carried away fast enough. The most common reasons are a failing internal pump that can't push the water around, or a build-up of sludge and debris that has created a physical blockage in the pipework. It can also be triggered by a large pocket of air trapped within the heat exchanger, preventing smooth water flow.
This issue often surfaces in autumn when the heating is turned on for the first time in months, as pump components can seize up or debris can settle during the summer period.
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.