BoilerFaultCodesTechnical description
The safety devices have been activated (lockout)
What causes this fault?
This fault occurs when the boiler's internal safety hardware detects that the heat exchanger has become dangerously hot. The most common reason is a lack of water flow or a blockage within the system, which prevents heat from being carried away from the boiler quickly enough.
This issue often surfaces during the first cold spell of autumn when the heating is turned back on and pumps or valves may have seized after months 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.
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