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 8 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