BoilerFaultCodesTechnical description
Circulation Fault (Primary Circuit)
What causes this fault?
This fault occurs when the boiler detects that water is not moving through the internal pipework quickly enough to carry heat away from the burner. The most common reasons are a failed internal pump, a blockage caused by system sludge, or a valve that has become stuck and is blocking the flow. Because the heat cannot escape, the boiler shuts down immediately to protect its internal components from melting or cracking.
This issue is frequently seen at the start of autumn when heating systems are turned back on after a summer of inactivity, which often causes moving parts like the pump to seize.
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.