BoilerFaultCodesTechnical description
Service Function: Max. heating output
What causes this fault?
This code appears because a service engineer has manually activated the 'chimney sweep' mode using the boiler's internal settings. It is not actually a fault, but rather a deliberate setting that forces the burner to run at full power so that gas pressure and emissions can be accurately tested. If you see this code and an engineer is not present, the service switch may have been left in the wrong position or bumped accidentally.
DIY fix possible
Locate the service buttons on the control panel.Press and hold the 'Reset' or 'Service' button for a few seconds to exit the test mode.Switch the boiler off and back on at the fused spur switch to reset the software.
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