305 Low

Worcester Bosch 305 Fault Code

The Worcester Bosch 305 fault code means: your boiler is temporarily pausing the hot water production to prevent itself from overheating or cycling on and off too frequently.. It appears on 23 Worcester Bosch models in our database.

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: Boiler in hot water anti-cycle mode

What causes the Worcester Bosch 305 fault?

This code appears when the boiler has reached its maximum internal temperature for hot water and needs to briefly shut down the burner to cool down. It is often caused by a lack of water flow through the heat exchanger, or because the taps have been turned on and off very quickly several times. By entering this mode, the boiler is simply protecting its internal components from excessive heat and wear.

This can be slightly more common in summer, as the incoming mains water is naturally warmer and the boiler reaches its target temperature much faster than in the winter.

DIY fix possible

Wait up to 15 minutes for the anti-cycle timer to expireEnsure hot water taps are fully closedCheck that the hot water temperature setting on the control panel is not set excessively high

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Worcester Bosch models that show the 305 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Worcester Bosch 305 fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026