High
Flue gas pressure switch on Biasi Prisma

Your boiler has detected a problem with how it safely vents exhaust fumes, which is preventing it from lighting to ensure your safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

Can temporarily stop the ignition of the burner but allow its ignition when the cause of the intervention has stopped.

From this model's manual
Verified against the Biasi Prisma installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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