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.

What the manual says

Manufacturer manual

Mains ON Only

From this model's manual
Verified against the Potterton Boiler Suprima 30l 100l installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like Green LED OFF, Red LED ON: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

Red LED FlashingView →

All 19 fault codes on the Prima 30B

Seeing a different code? Every code this model can display, in one place.

All lights: OFFFlashing Red LEDGreen LED ON, Red LED OFFGreen light 'On' onlyGreen light flashes rapidlyGreen light On onlyLockout (LED Mode)Lockout (rapid flashing)Overheat - Red LED: FLASHINGRED & GREEN lights flashingRED & GREEN lights OFFRed LED flashingRED LED on continuouslyRed LED on onlyRed LED rapid flashingRed LED: Flashing RedRed LED: Rapid FlashingRed light flashing (Lockout)

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 →