High Lockout
21 on Vokera Easi-Heat 29

Your boiler has lost communication with its external controls or is stuck in an internal testing phase, meaning it cannot start the heating cycle.

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

Temporary fault code (Refer to section 7.10)

What causes this fault?

This fault occurs when the boiler's main control board loses the electronic signal from the external timer or room thermostat, causing a break in communication. It can also happen if the boiler becomes stuck in an internal calibration mode after a power cut or a system reset. Essentially, the 'brain' of the boiler is waiting for a command to start that it can no longer hear.

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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