n4 High

Protherm n4 Fault Code

Also written as N4 — same fault.

The Protherm n4 fault code means: your boiler has identified a communication failure between the control panel and the main heating system, preventing it from operating correctly.. It appears on 1 Protherm model 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: 18 kW (61 416 Btu/hr)
Typical repair cost £150-300 (including labour)

Engineer required

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

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Protherm models that show the n4 fault code

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

Source

Protherm n4 fault code information on this page is sourced and cross-checked against the official Protherm service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026