Emergency
20 on Worcester Bosch Highflow 440 CDi

Your boiler is failing to ignite because it cannot properly receive or process the gas supply, meaning it is currently unable to provide heating or hot water.

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

Gas valve circuit / Ignition problem

From this model's manual
Verified against the Worcester Bosch Highflow 550 Cdi 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 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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