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d.21 on Glow-worm Flexicom 24c / 28c

Your boiler is currently indicating that the 'warm start' feature, which keeps water hot inside the unit for faster tap delivery, is being toggled or checked by the system.

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 domestic hot water

From this model's manual
Verified against the Glow Worm Flexicom 24c 28c installation & service manual, page 44.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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