BoilerFaultCodesYour boiler is temporarily pre-heating the internal water to ensure you get hot water quickly when you turn on a tap.
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: domestic hot water cycling mode active
What causes this fault?
This status occurs when the boiler's keep-hot function is activated to maintain a small reservoir of warm water inside the heat exchanger. It is a normal operation designed to reduce the time you have to wait for hot water to reach your taps. The boiler will fire up briefly even when you haven't turned on a tap to keep this internal temperature topped up.
DIY fix possible
Check if the 'Eco' mode is turned off; if off, the boiler will fire periodically to keep the heat exchanger warm.Press the 'Eco' button if you wish to disable this pre-heat feature and save energy.Observe the display; the S.20 code should disappear once the pre-heat temperature is reached.
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A boiler cover plan would cover faults like S.20 — no call-out fees, no surprises.
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