BoilerFaultCodesTechnical description
Primary flow fault
What causes this fault?
This fault occurs when the boiler's internal sensors detect that water isn't moving through the heat exchanger as quickly as it should, causing a sudden spike in temperature. The most common reasons are a failed or sticking circulation pump, a buildup of sludge blocking the pipes, or air trapped within the system preventing flow.
This code is frequently seen when heating is first turned on in autumn, as pumps can seize up after being left idle throughout the summer months.
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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