BoilerFaultCodesWorcester Bosch EF Fault Code
The Worcester Bosch EF fault code means: your boiler has detected that the water temperature is rising far too quickly for the amount of gas being used, which suggests water is struggling to circulate properly.. It appears on 10 Worcester Bosch models in our database.
Technical description: Central heating, boil detect. Large delta T despite minimum burner.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Worcester Bosch models that show the EF fault code
Click a model for the full fault code list and model-specific repair notes.
- 533 Compact
- 535 Compact
- Greenstar 25 Si Compact Repair: £150-350
- Greenstar 25Si Compact ErP Repair: £150-350
- Greenstar 27i System Compact ErP Repair: £150-350
- Greenstar 28CDi Compact ErP Repair: £150-350
- Greenstar 30 Si Compact Repair: £150-350
- Greenstar 30i System Compact ErP Repair: £150-350
- Greenstar 30Si Compact ErP Repair: £150-350
- Greenstar CDi Compact Repair: £150-300
Source
Worcester Bosch EF fault code information on this page is sourced and cross-checked against the official Worcester Bosch service / installation manuals for each affected model.
- Worcester Bosch 535 Compact manual (PDF)
- Worcester Bosch Greenstar 30 Si Compact manual (PDF)
- Worcester Bosch Greenstar 30Si Compact ErP manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026