E04 High

Biasi 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 10 Biasi models in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Phase-Neutral polarity inversion
Typical repair cost £80-160 (including labour)

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.

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.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026