Medium
F.104 on Viessmann Vitodens 200-W B2HF System

Your boiler has detected an error with an external electronic add-on, meaning it is unsure how to control certain heating or hot water features.

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

Depending on configuration of EM-EA1 extension (DIO electronics module)

From this model's manual
Verified against the Viessmann Vitodens 200 W B2hf System installation & service manual, page 91.
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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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