High Lockout
b1 on Viessmann Vitodens

Your boiler is currently stuck in an incomplete setup mode, meaning the installation process wasn't fully finished or the system hasn't been properly coded.

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

Installation in unfinished state - Fault during compression joint valve

What causes this fault?

This fault occurs when the boiler's internal computer has not been told exactly what type of heating system it is connected to. It is usually triggered if a technician replaced a part or installed the unit but didn't complete the final software configuration steps. Until this digital 'handshake' is finished, the boiler stays in a safe standby mode and refuses to fire up.

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

b0View →b8View →

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