High
266 on Worcester Bosch Greenstar 28CDi

Your boiler has detected that the water inside isn't circulating properly, likely because the pump is failing to move the water around the system as expected.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

CE No pressure variation detected after switching pump

From this model's manual
Verified against the Worcester Bosch Greenstar 28cdi Compact installation & service manual, page 65.
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 high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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