BoilerFaultCodesNavien E302 Fault Code
The Navien E302 fault code means: your boiler has detected that the water pressure inside the system is too low to run safely, so it has turned itself off.. It appears on 5 Navien models in our database.
Technical description: Insufficient water level in the boiler
DIY fix possible
Locate the external filling loop, which is a silver braided hose connecting two pipes underneath the boiler.Open the valves at both ends of the filling loop to allow cold mains water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close both valves tightly to stop the flow of water and ensure the silver hose remains attached but not leaking.
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Navien models that show the E302 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Navien E302 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