High
E21 on Biasi Advance Plus 16S 25S 30S

Your boiler has failed to ignite because it has detected an internal fault with the gas valve mechanism, meaning it cannot safely start heating your home.

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

Lockout EVG

From this model's manual
Verified against the Biasi Activ A installation & service manual, page 13.
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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