P23 Medium

Alpha P23 Fault Code

The Alpha P23 fault code means: your boiler is struggling to accurately measure the temperature of the hot water it is producing, which is likely preventing it from heating your taps or shower correctly.. It appears on 2 Alpha models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: DHW flow temp. (NTC)
Typical repair cost £120-220 (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 P23 fault code

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

Source

Alpha P23 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