Low
S.109 on Glow-worm Sustain 12s

Your boiler has entered a temporary sleep mode to save energy, meaning it is currently not heating your water or radiators.

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

Product's standby mode activated

From this model's manual
Verified against the Glow Worm Sustain 12s installation & service manual, page 33.
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

Check your thermostat or programmer to ensure it is set to 'On' or is currently in a timed heating periodPress the 'Reset' button on the boiler control panel onceEnsure there is no active holiday mode or energy-saving setting enabled on your external heating controller

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