E51 High

Alpha E51 Fault Code

The Alpha E51 fault code means: your boiler's internal computer has detected that the air fan installed is not the correct type or is communicating incorrectly, causing the system to stop for safety.. It appears on 7 Alpha models in our database.

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.

Technical description: Incompatible fan
Typical repair cost £220-£380 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Alpha models that show the E51 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Alpha E51 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026