Low
d.21 on Glow-worm Ultimate 3 25R

Your boiler is simply indicating that the 'warm start' feature, which keeps water hot for immediate use, is currently switched off or inactive.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

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.

What the manual says

Manufacturer manual

Status of the warm start for hot water

From this model's manual
Verified against the Glow Worm Ultimate 3 25r installation & service manual, page 29.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

DIY fix possible

Locate the hot water/warm start button or menu on your boiler's control panelToggle the setting to 'On' if you wish to have instant hot waterIf you prefer to keep it off to save energy, no action is required as this is a status message, not a fault

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d.20View →d.22View →

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