BoilerFaultCodesTechnical description
Flow temperature too high (STB)
What causes this fault?
This fault occurs when the water leaving the boiler exceeds a safe temperature limit, causing the system to shut down to prevent damage. The most common reason is a lack of water circulation, often caused by a failed pump or a blockage in the heat exchanger that prevents heat from being carried away quickly enough.
This issue is more frequent during the first cold spell of autumn when a pump that has been idle all summer may seize or struggle to move heavy sludge that has settled.
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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