BoilerFaultCodesTechnical description
The burner thermostat has been activated.
What causes this fault?
This fault occurs when the safety sensor near the burner detects excessive heat that could potentially damage the internal components. The most common reasons are a buildup of debris or limescale inside the main heat exchanger restricting water flow, or a localized 'hot spot' caused by a failing internal thermostat. It acts as a critical safety shutdown to prevent the appliance from overheating.
This issue often surfaces in winter when the boiler is running at maximum capacity for long periods, putting the heat exchanger under the most thermal stress.
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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