Low
34:0 on Viessmann Vitodens 300-W

Your boiler is receiving a constant request for heat from an outside control, which is causing all of your heating pumps to run at the same time.

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

Signal "External demand" on circulation pumps: All pumps are controlled

DIY fix possible

Check your room thermostat to ensure it is not set higher than current room temperature.Verify if an external heating controller or 'Summer/Winter' switch is stuck in the 'On' position.Try restarting the boiler using the main power switch to reset the external signal communication.

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