Medium
Blue light: On / Lockout: Off on Worcester Bosch Greenstar 25Si

Your boiler is working fine to heat your hot water, but it is failing to turn on when your radiators request heat.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Boiler not operating during central heating demand (HW ok)

From this model's manual
Verified against the Worcester Boiler 25si 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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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