BoilerFaultCodesNavien 84 Fault Code
The Navien 84 fault code means: your boiler's internal communication system is confused because two or more parts are trying to use the same digital identification signal.. It appears on 1 Navien model in our database.
Technical description: BSB address collision: More than 1 room units are assigned to the same HC
DIY fix possible
Identify all wall-mounted or wireless thermostats connected to your heating system.Check the configuration settings on each thermostat to ensure they are assigned unique zone addresses.Restart the boiler and your thermostat(s) to allow them to re-establish a conflict-free connection.
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Navien models that show the 84 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Navien 84 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