Medium
353 on Viessmann Vitodens 100-W B1GA

Your boiler is not receiving enough gas to run at full power, so it has automatically lowered its performance to stay operational.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Insufficient gas supply; burner output reduced

From this model's manual
Verified against the Viessmann Vitodens 100 W B1ga installation & service manual, page 58.
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 that your gas meter has credit (if using a pre-payment meter).Ensure your external gas emergency control valve is fully open.Check if other gas appliances, like a hob, are working correctly to rule out a wider supply issue.

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