Emergency
Pulsation on start on Worcester Bosch Greenstar Utility

Your boiler is struggling to burn fuel properly at start-up, which can cause vibrations and indicates an issue with the air supply or internal combustion settings.

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

CF - Flue draught incorrect; Combustion settings incorrect; Faulty nozzle

From this model's manual
Verified against the Worcester Bosch Greenstar Camray Utility 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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