High Lockout
e3 on Remeha Avanta 18V

Your boiler has detected an electrical safety issue where the power supply is not properly grounded or the internal control board has failed.

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

Mains supply not correctly earthed. Control unit or earth fault

What causes this fault?

This fault occurs when the boiler's internal computer detects that the electrical supply is missing a secure connection to the ground. The most common reason is a loose or corroded wire within the boiler itself, or a critical failure of the main control board which prevents it from sensing the electricity correctly.

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

E1View →E2View →E4View →

Related guides you might find useful

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Yellow or orange flame — CO safety

Safety-critical — turn off, read this.

Read →