F1 High

Protherm F1 Fault Code

The Protherm F1 fault code means: your boiler has stopped working because it is not receiving the necessary electrical power or an internal electrical safety fuse has blown.. It appears on 2 Protherm 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: Fault with mains supply or PCB fuse
Typical repair cost £120-250 (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 F1 fault code

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

Source

Protherm F1 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