BoilerFaultCodesYour boiler has shut down because the exhaust gases have become too hot, which is a safety measure to prevent damage to the internal components.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue Gas Temperature > 80°C for 5s, the Slave board shuts down
What causes this fault?
This fault occurs when the internal heat exchanger is failing to transfer heat effectively into the water, causing it to escape through the flue instead. The most common reasons are a heavy buildup of debris inside the heat exchanger or a lack of water flow, which prevents the system from cooling down properly. In some cases, it may simply be a faulty sensor incorrectly reporting that the exhaust is overheating.
This issue often surfaces during the first cold snap of winter when the boiler is forced to run at maximum capacity for long periods, putting more stress on the heat exchanger.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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