BoilerFaultCodesYour boiler is not broken; it is simply letting you know it is currently busy heating up your hot water cylinder or keeping its internal hot water supply ready for use.
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: Hot holding request / Cylinder charging request
What causes this fault?
This status occurs when the boiler detects that the water in your external hot water cylinder has cooled down and needs reheating. It can also appear if the boiler is pre-heating its internal components to Ensure you get hot water quickly when you turn on a tap. It is a normal part of the boiler's operation and simply means the unit is prioritising your hot water supply.
DIY fix possible
Check if your hot water timer is activeWait a few minutes for the boiler to finish the heating cycleTurn off 'Comfort Mode' on the front panel if you want to disable the pre-heat function
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like S.20 — no call-out fees, no surprises.
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