17 Medium

Unical 17 Fault Code

The Unical 17 fault code means: your boiler has temporarily stopped working because the electricity supply coming into your home has voltage or frequency levels outside of the normal safe operating range.. It appears on 2 Unical 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: FLAME CONTROL FREQUENCY BEYOND LIMIT. Depends on the power supply mains (Frequency and voltage beyond default limits). Wait for the values to return to the default limits
Typical repair cost £90-180 (including labour)

Engineer required

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

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Unical models that show the 17 fault code

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

Source

Unical 17 fault code information on this page is sourced and cross-checked against the official Unical service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026