BoilerFaultCodesVokera 48 Fault Code
The Vokera 48 fault code means: your boiler has shut down because the exhaust gases have become too hot, which is a safety measure to prevent damage to the internal components.. It appears on 1 Vokera model in our database.
Technical description: When the Flue Gas Temperature > 80°C for 5s, the Slave board shuts down
What causes the Vokera 48 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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Gas Safe Register →Vokera models that show the 48 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera 48 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026