Low
522 on Worcester Bosch Greenstar 8000 Style

Your boiler is currently running a self-diagnostic check to ensure its internal temperature sensors are reading accurately.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description

NTC Drift Test is running

DIY fix possible

Wait for the boiler to complete the test (usually 5-10 minutes)If the code persists, try resetting the boiler once via the touchscreen menuEnsure there is adequate water pressure (between 1 and 1.5 bar) on the display

Find a Gas Safe engineer
Search the official register →

Related fault codes

228View →

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

New boiler cost 2026

Realistic UK prices for a swap.

Read →