Emergency
352 on Viessmann Vitodens 100-W B1GA

Your boiler has shut down because it detected dangerously high levels of carbon monoxide during the combustion process.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

Combustion CO limit exceeded

From this model's manual
Verified against the Viessmann Vitodens 100 W B1ga installation & service manual, page 57.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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