High Lockout
E55 on Potterton Promax HE

Your boiler's internal computer has detected that its gas and air settings need recalibrating to ensure it burns fuel efficiently and safely.

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

Calibration required

What causes this fault?

This fault occurs when the boiler's control system detects that the gas-to-air ratio has drifted outside of its safe operating limits. It usually happens because the sensors can no longer automatically adjust the combustion, often due to a failing gas valve, worn ignition electrodes, or a fault within the main circuit board.

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.

Find a Gas Safe engineer
Search the official register →

Related fault codes

E28View →E53View →E160View →

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