High
51 on Worcester Bosch Highflow 440 CDi

Your boiler is failing to register a safe internal connection, which is preventing it from starting up reliably.

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

Portal not detected, ignition and reset control

From this model's manual
Verified against the Worcester Bosch Highflow 550 Cdi 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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