High
154 on Atag A200

Your boiler has detected that water is not circulating correctly through the system, causing it to shut down 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

The control system will, if an unacceptable temperature difference is detected, repeatedly try to establish a water flow. If this does not succeed, the boiler will block itself (code 154).

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

105View →

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 →