High Lockout
7F:0 on Viessmann Vitodens 300-W

Your boiler has detected an incorrect internal setting or a communication error between its electronic control boards.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Multi-occupancy house. Separate adjustment for holiday program and time program for DHW loading, as option

What causes this fault?

This fault occurs when the boiler's internal computer module fails to communicate correctly with the rest of the heating system. It is usually caused by an electrical component failure on the main circuit board or a corruption in the boiler's specific software settings. Hardware wear and tear or a power surge can often trigger this total system shutdown.

Engineer required

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

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Related fault codes

7F:1View →F9View →

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