Navien tankless water heater error codes

Navien tankless water heater code E004

False flame detection: the heater senses a flame that should not be there.

Note whether the heater shuts down right after a tap is opened.

Navien's checks: the ground wire is connected and the igniter is checked for spark. Ground and igniter work is for a licensed professional.

Navien tankless water heater code E012

Flame loss.

Check that the main gas valve is open.

Navien's checks: the main gas line valve is open, gas pressure is within range, the gas meter has proper BTU capacity, the flame rod (its value in diagnostic mode), the intake air filter, the ground wire, the power supply, and the ground connection screws on the heat exchanger.

Navien tankless water heater code E030

Exhaust overheat: the exhaust limit sensor shuts down the unit when the flue temperature exceeds 230 degrees Fahrenheit (110 degrees Celsius) for more than 10 seconds.

Turn the heater off for at least 30 minutes, as Navien directs, then restart once.

Navien's checks: clean the inlet water filter, check the exhaust thermistor and its value in diagnostic mode, the dipswitch settings, the water adjustment valve, and the heat exchanger, where a flush may be necessary.

Navien tankless water heater code E047

Abnormal exhaust thermistor. Sub-code 1 is an open circuit and sub-code 2 is a short.

Navien's action for sub-code 1 is to check the exhaust thermistor connection, and for sub-code 2 to check for a proper connection to the PCB.

Navien tankless water heater code E109

Abnormal fan motor activity.

Check the intake air filter for lint and dust.

Navien's checks: check and clean the intake air filter, verify proper voltage and wire connection, and check and clean the fan motor.

Navien tankless water heater code E110

Exhaust blockage. Sub-code 1 is found by checking the fan, sub-code 2 when using hot water and sub-code 3 when using space heating.

Check the intake, exhaust and condensate drain pipes for ice, snow or wildlife.

Navien directs checking the intake, exhaust and condensate drain pipe for obstructions such as ice, snow or wildlife, and checking and cleaning the intake air filter. For sub-code 3 the manual lists restarting the unit and removing the front cover as a temporary diagnostic step for a technician, to see whether the blockage is in the air path. It is a test, not a fix, and the heater should not be left running with its cover off.

Navien tankless water heater code E407

Abnormal hot water outlet thermistor. Sub-code 1 is open and sub-code 2 is short.

Navien's actions: check the thermistor, and replace the thermistor.

Navien tankless water heater code E421

Abnormal cold water inlet thermistor. Sub-code 1 is open and sub-code 2 is short.

Navien's actions: check the thermistor, verify its value in diagnostic mode, and replace the thermistor.

Navien tankless water heater code E432

Abnormal cold water inlet 2 thermistor. Sub-code 1 is open and sub-code 2 is short.

Navien's actions: check the thermistor, check the thermistor voltage and resistance values, and replace the thermistor.

Navien tankless water heater code E434

Abnormal water adjustment valve. Sub-code 1 is open and sub-code 2 is close.

Note whether water flow at taps is weak or the temperature swings.

Navien's action: check the water adjustment valve.

Navien tankless water heater code E438

Abnormal circulation pump, on A models only.

Check that the recirculation loop valves are open.

Navien's checks: the circulation pump, water filter for blockage, the flow sensor, the cold water main line, and set the unit to Internal Recirculation mode and verify the flow rate.

Navien tankless water heater code E439

Abnormal flow sensor.

Check that the cold-water supply valve to the heater is fully open.

Navien's action: check the flow sensor.

Navien tankless water heater code E441

Abnormal hot water inlet 2 thermistor. Sub-code 1 is open and sub-code 2 is short.

Navien's actions: check the thermistor and replace the thermistor.

Navien tankless water heater code E445

Abnormal mixing valve. Sub-code 1 is open and sub-code 2 is close.

Note whether the water temperature at taps is unstable.

Navien's action: check the mixing valve.

Navien tankless water heater code E517

Abnormal dip switch setting.

Do not change any dip switch yourself.

Navien's action: check the dip switches on the front panel and PCB.

Navien tankless water heater code E593

Abnormal panel key.

Check that no front-panel button is stuck or held down.

Navien's action: check the panel.

Navien tankless water heater code E594

Abnormal input data. Sub-code 0 is the heat exchanger high limit switch, 1 the exhaust sensor, 2 the flame rod, 3 to 14 abnormal PCB memory, 15 a pressure sensor reading below range and 16 a pressure sensor reading over range.

Reset the heater once from its front panel.

Navien's actions: check the PCB (sub-codes 0 and 3 to 14); the exhaust sensor wiring connection and the exhaust sensor (1); the flame rod wiring connection and the flame rod (2); the pressure sensor wiring connection and the sensor's output voltage (15 and 16).

Navien tankless water heater code E736

Abnormal cascade communication.

Check that the heaters in the cascade are all powered.

Navien's checks: the Ready-Link cable, the cascade settings, and PCB version compatibility.

Navien tankless water heater code E760

A flushing or service alarm: Navien says a heat exchanger flush is necessary.

Note when the heater was last flushed and whether the water is hard.

Navien's action: a heat exchanger flush is necessary. If the solution does not resolve a problem, Navien's manual says to contact Navien's Technical department.