n1 Low

Protherm n1 Fault Code

Also written as N1 — same fault.

The Protherm n1 fault code means: your boiler is currently operating in its base 10kw heating mode, which is a standard status indicator rather than a fault, meaning the appliance is functioning correctly.. It appears on 1 Protherm model 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: 10 kW (34 120 Btu/hr)

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 n1 fault code

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

Source

Protherm n1 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