15 + High

Biasi 15 + Fault Code

Also written as 15 — same fault.

The Biasi 15 + fault code means: your boiler has likely stopped working because water is not moving through the system quickly enough to prevent it from overheating.. It appears on 4 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: Probable insufficient circulation.
Typical repair cost £150-350 (including labour)

DIY fix possible

Check that your central heating valves (lockshields) are fully openEnsure at least one or two radiators are turned to maximumBleed your radiators to remove any trapped airCheck that the boiler pressure is between 1.0 and 1.5 bar

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Biasi models that show the 15 + fault code

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

Source

Biasi 15 + 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 27 April 2026