High
342 on Worcester Bosch Greenstar 28CDi

Your boiler is heating the water much faster than it is able to move it away, causing the system to stop as a safety precaution to prevent overheating.

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

Temperature rise during hot water mode too rapid

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 →

No hot water but heating works

Almost always a stuck diverter valve on combis.

Read →

Boiler keeps cutting out

Lockout fault with a reset-needed pattern.

Read →