Low
F.666 on Viessmann Vitodens 222-F B2TF

Your boiler is struggling to communicate with a specific temperature sensor related to your solar hot water heating system.

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

No solar function with preheating active. Lead break, DHW preheating sensor TS3.

From this model's manual
Verified against the Viessmann Vitodens 222 F B2tf installation & service manual, page 107.
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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Related fault codes

F.667View →F.668View →

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