17 Medium

Unical 17 Fault Code

The Unical 17 fault code means: your boiler has detected an issue with the electrical power supply coming into your home, meaning the voltage or frequency is currently unstable for the unit to operate safely.. 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)
Typical repair cost £0-120 (including labour)

DIY fix possible

Turn the boiler off using the main power switch or at the fused spur wall switch.Wait for approximately 30 seconds.Turn the power back on and check if the error clears once the system reboots.

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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 7 July 2026