BoilerFaultCodesWhat the manual says
Manufacturer manualMax. output (hotwater - combi only)
What causes this fault?
This code appears when the boiler detects a high demand for hot water, causing it to ramp up to its full heating capacity. It is physically triggered by the internal flow sensor detecting water movement, which tells the burner to provide maximum heat to your taps. While usually just a status update, if it stays on without you running a tap, it could mean a component like the diverter valve is stuck or leaking.
This code is slightly more frequent in winter when incoming mains water is much colder, forcing the boiler to work at maximum power for longer to reach the desired temperature.
DIY fix possible
Check if any hot water taps are fully turned on and close themPress the Reset button once to clear the display if the code persistsMonitor the boiler to see if the code disappears after hot water use ends
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Related fault codes
All 365 fault codes on the Greenstar CDi Compact
Seeing a different code? Every code this model can display, in one place.