High Lockout
46 on Vokera Condexa Pro

Your boiler has shut down because it has detected that the water leaving the unit is getting too hot, which is usually caused by a circulation problem.

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

When the Outlet Temperature > 90°C for 5s, the Slave board shuts down

What causes this fault?

This fault occurs when the water inside the boiler heats up too quickly and cannot be moved away into your radiators or hot water cylinder. The most common reason is a failed circulation pump or a blockage in the system, such as a build-up of sludge or limescale, which prevents the heat from being safely dispersed.

This issue is more frequent in autumn when heating systems are switched back on after a long summer break, as pumps can seize up due to inactivity.

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

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

Radiators cold at the bottom

Sludge build-up — needs flushing, not bleeding.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →