FD 231 on a Worcester Bosch boiler means: mains power interruption. The boiler has lost, or is unhappy with, its electrical supply.
On some older Worcester boilers FD simply means the reset button was pressed by mistake — pressing reset again clears it.
This code applies to Worcester Bosch Greenstar Si Compact, Greenstar i and CDi Compact. Codes can mean different things on different models, so check the display against your boiler's user manual.
What you can safely check
- Check the fused spur and your consumer unit (fuse box) for a tripped switch or blown fuse.
- If there has been a power cut, the boiler may just need resetting once.
When to call an engineer
If the code keeps appearing, ask a Gas Safe engineer to check the boiler, or an electrician to check the supply to it.
Never remove the boiler casing yourself — everything behind it must be handled by a Gas Safe registered engineer. If you smell gas, open windows, turn the gas off at the meter, and call the National Gas Emergency number on 0800 111 999.
Repair it, or replace it?
If your boiler is over 10 years old, compare a repair against a new combi before you pay for parts.
Applies to: Worcester Bosch Greenstar Si Compact, Greenstar i and CDi Compact
Meaning checked against: Heatable — Worcester Bosch error codes
Last reviewed November 2026. Always follow your boiler's own user manual.