BoilerFaultCodesBiasi E04 Fault Code
The Biasi E04 fault code means: your boiler has detected that the electrical wiring in your home or the plug is connected the wrong way round, preventing it from starting safely.. It appears on 12 Biasi models in our database.
Technical description: Phase-Neutral polarity inversion
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Biasi models that show the E04 fault code
Click a model for the full fault code list and model-specific repair notes.
- Activ A Repair: £80-150
- Activ A Repair: £80-150
- Advance Plus 16S 25S 30S Repair: £0-120
- Advance Plus 16S 25S 30S Repair: £80-150
- Antares Combi Repair: £80-160
- Antares System Repair: £100-£350
- Basica Combi Repair: £100-£350
- Basica System 2022 Repair: £100-£220
- Dina Repair: £0-160
- Inovia 2020 Repair: £0-250
- Inovia 2020 Repair: £80-160
- Rinnova Adaptive Combi Repair: £0-120
Source
Biasi E04 fault code information on this page is sourced and cross-checked against the official Biasi service / installation manuals for each affected model.
- Biasi Activ A manual (PDF)
- Biasi Advance Plus 16S 25S 30S manual (PDF)
- Biasi Antares Combi manual (PDF)
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026