BoilerFaultCodesTechnical description
Safety sensor of the heat exchanger is overheated.
What causes this fault?
This fault occurs when water cannot travel through the boiler fast enough to take the heat away, causing the internal temperature to spike. The most common reasons are a failed pump that isn't pushing water round or a blockage caused by a buildup of sludge and debris in the system. Small air pockets trapped within the heat exchanger can also trigger this safety shutdown.
This issue often appears when the heating is first turned on in autumn, as pumps can seize up after being inactive over 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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