Low
4-b5 on Worcester Bosch Greenstar 2000

Your boiler is notifying you that its internal protection against freezing has been activated or deactivated, which is a normal safety monitoring function.

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

Device frost protection: OFF: switched off, ON: switched on.

DIY fix possible

Check your home temperature is above 5°CEnsure the boiler power supply remains switched onMonitor the display to see if the code clears once the unit reaches a safe temperature

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