BoilerFaultCodesYour boiler has detected that water is moving too slowly or in the wrong direction through the system, causing the pipes to heat up unevenly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Return greater than flow – flow temperature increases too fast
What causes this fault?
This fault occurs when the boiler's internal sensors detect that the water leaving the unit is cooler than the water coming back, or that the temperature is rising far too quickly. This typically points to a circulation failure where the water is either stuck or moving too slowly to carry heat away from the burner. The most common reasons are a seized pump, a blockage in the pipework, or air trapped within the heat exchanger.
This fault is more frequent in autumn when heating systems are turned on for the first time after summer, as pump components can seize during long periods of inactivity.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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