Low
I.56 on Viessmann Vitodens 200-W B2HF System

Your boiler is receiving a signal from an external control, like a thermostat or heat pump, telling it to run and provide heat.

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

External demand active

From this model's manual
Verified against the Viessmann Vitodens 200 W B2hf System installation & service manual.
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 if your room thermostat is set to a high temperatureVerify if your hot water timer is currently activeCheck for any external smart home apps that might be requesting heat

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