High
Green LED OFF, Red LED ON on Potterton Prima 30B

Your boiler is receiving power but has entered a lock-out state, meaning it has detected an internal issue and stopped working to keep your home safe.

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 ON Only

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

Red LED FlashingView →

Related guides you might find useful

Pilot light keeps going out

Older boilers — thermocouple, draught, gas supply.

Read →

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 →