BoilerFaultCodesYour boiler is currently working at its maximum power setting to meet a high demand for heating or hot water, which is a normal operational signal rather than a malfunction.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: 2nd stage operating indicator (high fire). Indicates high fire in operation.
What causes this fault?
This code appears when your boiler's burner switches to its highest output level to quickly reach the desired temperature for your radiators or hot water. It simply confirms that the internal gas valve is fully open and the system is working at peak performance to satisfy a high demand. Once the water temperature gets closer to your setting, the boiler will naturally ramp down to a lower power level.
This display code is more frequent during the winter months when the boiler has to work much harder to heat up very cold water entering the house.
DIY fix possible
Check if your thermostat is set very highWait for the boiler to reach the desired temperature, at which point the light should go outEnsure all radiator valves are open if you have requested heating
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A boiler cover plan would cover faults like B5 — no call-out fees, no surprises.
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