High
2966 on Worcester Bosch Greenstar 8000 Life GR8300iW 35 S

Your boiler has detected that the water inside is heating up far too quickly, usually because water is not flowing properly through the system.

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

Flow temperature rise in heat exchanger too rapid 1. System is not filled with water. 2. No water flow, because CH system is closed. 3. No water flow, because pump is not operating correctly.

From this model's manual
Verified against the Worcester Bosch/Worcester Bosch 8000 Life System 2 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 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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Related fault codes

2965View →2967View →EAView →

All 21 fault codes on the Greenstar 8000 Life GR8300iW 35 S

Seeing a different code? Every code this model can display, in one place.

10371065106810731074107510762920292429252927294629482950296329642965296729702971

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