Low
d.23 on Glow-worm Sustain 12s

Your boiler is currently waiting for a signal from your thermostat or timer to tell it to start heating your home or water.

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 heating demand

From this model's manual
Verified against the Glow Worm Sustain 12s installation & service manual, page 30.
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 room thermostat is set to a temperature higher than the current room temperature.Ensure your external timer or programmer is set to 'On' for central heating or hot water.Wait a few minutes to see if the boiler initiates the heating cycle automatically.

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Related fault codes

d.24View →d.25View →

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