2921 - Low

Worcester Bosch 2921 - Fault Code

Also written as 2921 — same fault.

The Worcester Bosch 2921 - fault code means: your boiler has been left in a professional testing mode, meaning it is currently running at a fixed output rather than responding to your heating controls.. It appears on 6 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 electr. in test mode
Typical repair cost £0-80 (including labour)

DIY fix possible

Locate the reset button on the front control panel.Press and hold the reset button for approximately 3 to 5 seconds.The display should return to the normal temperature reading and resume standard operation.

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Worcester Bosch models that show the 2921 - fault code

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

Source

Worcester Bosch 2921 - 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