122 Medium

Navien 122 Fault Code

The Navien 122 fault code means: your boiler's secondary heating zone is failing to reach the required temperature, likely because the system is struggling to circulate heat to a specific part of your home.. It appears on 1 Navien model 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: Flow temp HC2: Flow temperature set point hc2 not reached
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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Navien models that show the 122 fault code

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

Source

Navien 122 fault code information on this page is sourced and cross-checked against the official Navien service / installation manuals for each affected model.

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