BoilerFaultCodesYour boiler's pre-heat function for hot water isn't reaching the temperature it expects, which may lead to slower or inconsistent hot water delivery.
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: Difference between warm start and hot-water outlet target value
What causes this fault?
This fault occurs when the boiler struggles to keep its internal store of hot water at the correct temperature for the 'warm start' feature. The most common reasons are a buildup of limescale in the heat exchanger or a failing sensor that is giving the control board inaccurate temperature readings.
This issue is more noticeable in winter when the incoming mains water is much colder, forcing the boiler to work harder to maintain its pre-heat temperature.
DIY fix possible
Check if the hot water temperature dial on the front of the boiler is set too lowTurn the boiler power off and back on to reset the electronicsEnsure all hot water taps are fully closed and not dripping
Find a Gas Safe engineer
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A boiler cover plan would cover faults like d.73 — no call-out fees, no surprises.
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