P15 Low

Alpha P15 Fault Code

The Alpha P15 fault code means: your boiler is receiving an incorrect or inconsistent signal from the weather sensor installed outside your home, which may affect how the heating adjusts to the outside temperature.. It appears on 2 Alpha models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: External sensor offset
Typical repair cost £100-180 (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 P15 fault code

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

Source

Alpha P15 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 7 July 2026