High Lockout
E0 on Viessmann Vitodens 100-W

Your boiler has shut down because an external safety device, such as a thermostat or water pressure switch, has detected a potential issue and stopped the burner from firing.

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

Burner blocked, fault in the external safety chain

What causes this fault?

This fault occurs when an additional safety device outside the boiler's main control board breaks the electrical circuit to prevent damage. It is usually triggered by a secondary sensor detecting that the system pressure is too low or that the water temperature has exceeded a safe limit. Essentially, an external 'shout' has told the boiler to stop firing for your safety.

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

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