BoilerFaultCodesTechnical description
Primary flow fault
What causes this fault?
This fault occurs when water is unable to move through the boiler's heat exchanger quickly enough to safely carry heat away. The most common reasons are a failing circulation pump that can no longer push the water, or a physical blockage caused by a build-up of sludge and debris within the system pipework.
This issue frequently appears during the first cold spell of autumn when the heating is turned back on after being idle all summer, which can cause internal pump parts 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.
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