C3 (ΔP-C) High

Alpha C3 (ΔP-C) Fault Code

Also written as C3PC — same fault.

The Alpha C3 (ΔP-C) fault code means: your boiler has detected an issue with the internal water pressure or circulation flow, meaning it cannot safely heat your home or water.. It appears on 4 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: Constant curve - H=3 m (White LED)
Typical repair cost £150-350 (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 C3 (ΔP-C) fault code

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

Source

Alpha C3 (ΔP-C) 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