High
b1 on Worcester Bosch Greenstar 25i (ZWB 7-25)

Your boiler is struggling to recognise one of its internal electrical components, which is preventing it from starting up correctly.

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

Keyed plug not detected.

From this model's manual
Verified against the Worcester Bosch Greenstar 25i Zwb 7 25 installation & service manual, page 43.
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

b2View →e9View →

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