Emergency
109 on Ariston Clas ONE R

Your boiler has too much water pressure inside the system, causing it to shut down for safety.

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

High primary circuit pressure (> 3 bar)

From this model's manual
Verified against the Ariston Clas One R installation & service manual, page 34.
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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