Emergency
A20 on Ariston Genus 24 MFFI

Your boiler has detected a flame inside the combustion chamber before it actually turned on the gas supply, implying a potential sensor or ignition system error.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

What the manual says

Manufacturer manual

The flame was detected before the gas valve opened

From this model's manual
Verified against the Ariston Genus 24 Mffi Combi installation & service manual, page 47.
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 emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

A21View →A22View →

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