High
0 (Flashing) on Potterton Envoy 30

Your boiler has stopped working because it failed to ignite or got too hot, and it now needs a manual reset to try and start again.

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

Boiler at Lock-Out. Indicates burner failing to light during a start sequence or a high temperature being recorded.

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 guides you might find useful

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →