Low
Viessmann boilers on Viessmann A8

Your boiler is operating in a manual override or temporary control mode, often meaning it is ignoring external thermostat signals to keep the heating running.

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.

Technical description

Control mode

DIY fix possible

Check your external thermostat or smart controls are turned on and connectedEnsure the boiler control knob is not turned to a test or manual settingPerform a simple reset by turning the power off and back on at the fused spur

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