Navien NPE Error Codes: What Each One Means
Navien's NPE condensing tankless water heaters (NPE-150S, -180A/S, -210A/S, -240A/S) show an error code on the front panel when something stops them working. Navien's own user's information manual lists every code with a reason and an action. This is that table, grouped by type; where Navien's action is to contact technical support, that is the right next step.
Ignition and flame: E003, E004, E012
E003 is ignition failure: Navien's check is that the main gas supply valve is open. If it is open and E003 returns, or you smell gas, stop and call a licensed technician. E004 is false flame detection: Navien says to make sure the electrical cord is properly grounded. E012 is flame loss: clean the intake air filter (Navien's manual, page 13) and make sure the electrical cord is properly grounded.
Overheating: E016 and E030
E016 is overheating of the heat exchanger. E030 is exhaust overheating: the water heater shuts down when the flue temperature exceeds 149 °F (65 °C). For both, Navien's actions are to turn the system off for at least 30 minutes and restart it, clean the cold water inlet filter (page 12), and flush the heat exchanger (page 11).
Air and fan: E109 and E110
E109 is abnormal fan motor operation: Navien says to clean the intake air filter. E110 is abnormal air pressure: make sure the exhaust pipe is free of obstructions, and clean the intake air filter.
Recirculation: E438
E438 is abnormal circulation pump operation. If you use external recirculation, Navien says to make sure all water supply and return lines are open; with internal recirculation, check the direction of the 2-way valve.
Sensors and valves: call technical support
For these codes Navien's action is to contact its technical support: E407 hot water outlet thermistor open or short circuit, E421 cold water inlet 1 thermistor, E432 cold water inlet 2 thermistor, E441 hot water inlet 2 thermistor, E434 water adjustment valve, E439 flow sensor, E445 bypass mixing valve, E785 flow switch or sensor, and E740 outdoor temperature sensor.
Controls and limits: call technical support
E046 limit control, E047 exhaust thermostat, E060 dual venturi, E517 DIP switch setting, E593 front panel key, E615 input and memory, E736 cascade communication and E782 main panel communication all go to Navien technical support. E515 is abnormal PCB operation: Navien's first check is that the electrical cord is properly grounded.
E760: time to flush
E760 is not a fault: it is the flushing and service alarm. Navien's action is to contact your installer to perform routine service.
If the code comes back
Navien's manual ends the table with one instruction: if these remedies do not resolve the problem, contact its technical support. The number is printed on the same page of the manual. Gas, venting and electrical repairs on a tankless water heater are for a licensed technician.
Related Error Codes
FAQ
Ignition failure. Navien's manual says to make sure the main gas supply valve is open. If it is open and the code returns, call a licensed technician.
It is the flushing and service alarm, not a fault. Navien says to contact your installer to perform routine service.
Abnormal air pressure. Navien's checks are that the exhaust pipe is free of obstructions and that the intake air filter is clean.
Sources
Documents this guide was checked against. How we verify.
Always unplug an appliance and shut off its water supply before servicing. This guide is informational and not a substitute for a qualified technician.