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Navien Water Heater Error Codes

Navien is a leading manufacturer of condensing tankless water heaters and their tankless products are some of the best and most reliable systems in Canada. Even products from top market brands can experience some problems from time to time. Nothing in this world is perfect, nor are the HVAC systems.

Navien tankless water heaters can show error codes on their display to help you identify the problem. Some of the common codes are listed below:

Navien Tankless Water Heater Error Codes

E003 - Ignition Failure

Error Occurnace Conditions

In the event of an ignition failure, the water heater will attempt ignition 10 times. If no flame is detected, the system displays the error message E003 (manually cleared) on the remote controller.

Action

Check if the gas supply valve is open and for proper supply pressure.

Check the electrode gap, electricity discharge, or deformation of the flame rod.

Check the operation of the ignition transformer (ignition state, input power (AC 102~132 V)

Check the operation of the gas control valve (DC 22~24 V, coil short circuit, solenoid valve).

Check the flame rod, wiring and grounding.

Check if the air pressure hose is broken or clogged.

Check if the air pressure sensor works properly.

Check the PCB DIP switch settings.

Adjust the offset pressure.

Check the gas orifice plate for the proper gas type.

Check the flue and air supply for any collected water (for vertical vent installations).

Tighten the ground connection screws on heat exchanger.

E004 - False Flame Detection

Error Occurnace Conditions

Pre ignition false-flame
If a flame signal is detected continuously for 3 seconds before combustion (stand-by, pre-purge, preignition), a false-flame error E004 (automatically cleared) is displayed on the front panel and the system
performs continuous post-purge and operates the pump

Post purge false-flame
If a flame signal is detected continuously for 3 seconds when the system performs post-purge as fuel supply
is stopped, a false-flame error 004E (automatically cleared) is displayed on the front panel and the system
performs continuous post-purge and operates the pump.

Action

Check if gas leaks due to defective seals on the main gas valve.
Check if proper spark is discharged from the electrode.
Check if gas is supplied within the proper pressure range.
Check the PCB and replace if defective.

E012 - False Flame Loss

Error Occurnace Conditions

If Navien tankless system detects loss of flame during combustion, it stops supplying fuel, attempts to restart, counts the incidents of flame loss, and if the incident occurs 20 times consecutively displays 012E (manually
cleared) on the front panel.

Action

Measure the gas supply pressure (NG: 3.5″ ~ 10.5” W.C, LP: 8”~ 13.0″ W.C)
Check the Gas meter Capacity.
Tighten the ground connection screws on heat exchanger.
Check if the gas orifice is clogged.
Check if Dual Venturi is operating properly.
Check if the PCB is working properly

E016 - Overheating of Heat Exchanger

Error Occurnace Conditions

If the overheat controller on the heat exchanger is initiated during  combustion/standby of the water heater, the
system displays the 016E (manually cleared) message on the front panel. The water heater switches into LockOut, and performs post-purge continuously and operates the pump

Action

Clean the inlet water filter.
Check High Limit Switch.
Check for proper dip switch settings.
Check the water adjustment valve.
Check the heat exchanger; a flush may be necessary.
Check pump operation (for A models only).
Turn OFF the system for at least 30 minutes then restart.

E030 - Abnormal Exhaust Gas

Error Occurnace Conditions

If the overheat controller on the top of the exhaust duct is initiated, the system displays the heat exchanger bimetal overheat message 30E (cleared manually) on the front panel.
The water heater switches into Lock-Out, and performs post-purge continuously and operates the pump.

Overheating controller operates when the temperature exceeds 230°F (110°C) for 10 minutes or over.

1. When the controller detects the exceeding temperature of 230°F (110°C) for 10 minutes or over, “E030” error
code will display and perform post-purge. It will be automatically cleared.
2. When the controller detects the exceeding temperature of 140°F (60°C) while performing post-purge.
It must be manually cleared.

3. When the controller detects the exceeding temperature of 230°F (110°C) for 10 seconds or over three times or more after the error is automatically cleared. It must be manually cleared.

Action

Turn OFF the system for at least 30 minutes then restart.
Clean the inlet water filter.
Check exhaust thermistor and verify [K] value in DIAGNOSTIC mode.
Check for proper dip switch settings.
Check the water adjustment valve.
Check the heat exchanger; a flush may be necessary.

E031 - Overheating of Burner

Error Occurnace Conditions

Fault code e031 indicates that the burner has overheated. The burner can be overheated. If the burner becomes blocked with fuel residue, it may overheat.

Action

Check the overheating fuse of the burner.
Follow the actions for E016 and E030 error codes.

E046 - Abnormal Operation: Limit Control

Error Occurnace Conditions

Heat exchanger overheated –The error occurs due to high exhaust gas temperature caused by a damaged or clogged heat exchanger.

Action

Flush the heat exchanger to remove scale deposits.
Replace the heat exchanger if it is damaged or cannot be unclogged.

Defective overheat controller – Defective contact point of the exhaust gas overheat controller 230°F (110°C) Max

Action

Check connection of the overheat controller.
If the resistance is abnormal, replace the temperature sensor.
Check the output temperature displayed on the PCB.

Other trouble – Defective PCB

Action

If the issue continues despite checking the items above, replace the PCB.

E047 - Abnormal Operation: Exhaust Thermostat

Error Occurnace Conditions

The error occurs when exhaust thermistor is not operating normally.

Action

Check exhaust thermistor connection.
Check for proper connection to the PCB.
Check heat exchanger
Replace exhaust thermistor if necessary

E060 - Abnormal Operation: Dual Venturi

Error Occurnace Conditions

This error message is displayed on the front panel if the wiring is disconnected or the Dual Venturi malfunctions.

The water heater switches into Lock-Out, and performs post-purge continuously and operates the pump.

Action

Check the Dual Venturi connection.
Test Dual Venturi for proper operation using TEST mode.
Check gas orifice for obstructions.

Error Code E109 - Abnormal Operation: Fan Motor

Error Occurnace Conditions

The system checks the RPM signal after the fan starts to run, and displays the error message 109E (cleared
manually) in the following cases:

– If the RPM remains low or close to 0, the system determines RPM error, and the water heater switches into
Lock-Out (gas valve and ignition transformer locked). (However, the air pressure sensor should be normal.)

– If the RPM signal of low or close to 0, is detected for 3 seconds during combustion, the system stops
combustion, and the water heater switches into Lock-Out. (However, the air volume sensor should be
normal.)

Action

Check if the fan motor works normally using the component test mode.
Check the power supply to the fan (Black + Red, approx. DC 127~184 V)
If RPM is significantly low while the fan works and the power supply is normal, replace the fan motor.
If the fan connector is wet due to any reason including leakage, take corrective action by powering the unit OFF, then drying the components completely before continuing operation.
Check for loose connection of white connector that attaches the fan motor to the PCB.

Error Code E110 - Abnormal Air Pressure

Error Occurnace Conditions

The system senses the air volume and the RPM signal, and displays 110E on the front panel in the following cases:

– When the initial fan auto-adjust is not performed.

– When the unit capacity reaches up to 95% of the maximum heat during combustion, and APS is not up the standard value.

Action

Check if the venturi (burner) hole is clogged.
Check if the condensation drain line or the drain is clogged.
Check the flue and exhaust to verify proper installation and clearances. (Circulation of exhaust gas generates noise.)
Check if the air supply/exhaust flue is clogged (rainwater may collect inside from an improperly installed air supply/exhaust pipe).
Defective air pressure sensor or PCB.

Error Code E407 - Hot water Outlet: Thermistor Open or Short Circuit

Error Occurnace Conditions

If an error (open: 14°F (-10°C) or lower) in the Hot water outlet temperature sensor is detected, the system displays the 407E error on the front panel. If this occurs, the water heater initiates shutdown.

Action

Check if the Hot water outlet temperature sensor connector is wet due to any reason, including leakage.
Check the Resistance of the Hot water outlet temperature sensor.
Replace the defected Hot water outlet temperature sensor.
Replace the controller.

Error Code E421 - Cold water inlet1: thermistor open or short circuit

Error Occurnace Conditions

If an error (open: 14°F (-10°C) or lower) in the heat exchanger input temperature sensor is detected, the system displays the 421E error on the front panel. If this occurs, the water heater initiates shutdown.

Action

Check if the heat exchanger input temperature sensor connector is wet due to any reason, including leakage.
Replace the defected heat exchanger input temperature sensor.
Replace the controller.

Error Code E432 - Cold water inlet2: thermistor open or short circuit

Error Occurnace Conditions

If an error (open: 14°F (-10°C) or lower) in the cold water temperature sensor is detected, the system displays the 432E (cleared automatically) error message on the front panel. The water heater initiates shutdown mode.

Action

Check if the cold water temperature sensor is open and if the connector is attached properly.
Check the defect of the cold water temperature sensor.
Defective PCB

Error Code E434 - Water Adjustment valve error

Error Occurnace Conditions

If the water adjustment valve does not work properly due to a defective feedback sensor, water adjustment valve, or PCB board, the system displays 434E (cleared automatically/manually).<only when in CASCADE mode>

– Water adjustment valve error – The system commands opening of the water adjustment valve, but the valve remains closed. [Check the feedback sensor.] (Cleared manually)

– If the Water adjustment valve sensor open/short-circuit is detected, the system displays an error message. If flow is sensed, the system clears the error automatically and provides the hot water. If open/short-circuit is detected after hot water is used, the system displays the error message.

Action

If the 434 error occurs, connect the Water adjustment valve to the PCB. The valve must be kept open when the water heater is not operating. If the PCB is defective, the motor keeps operating and the valve continues to make attempts to open/close.

Defective water adjustment valve
Defective PCB
Check the operation of the water adjustment valve using the Component Test mode.

Error Code E438 - Abnormal operation: circulation pump (in case of installed AHU)

Error Occurnace Conditions

Connect the power, start the pump, and check if the system senses water flow.
If flow is not sensed after the pump has started, the system displays 438E (cleared automatically) on the front
panel.

Action

Defective flow sensor.
Defective pump.
Check water filter for debris.
Check for locked air in the pump.
Defective PCB.
Check the operation of the pump and flow sensor using the Component Test mode.

Error Code E439 - Abnormal operation: flow sensor

Error Occurnace Conditions

As one or more units are operating in the cascade system, if no flow is detected while the system opens the water adjustment valve, the system considers it as a defective flow sensor. The system displays 439E (cleared manually) on the front panel and switches the unit operation into the Lock-Out mode (gas valve and ignition transformer locked).

Action

Check the supply of cold water while the cascade system is disabled. (frozen/locked valve).
Defective flow sensor.
Defective PCB.

Error Code E441 - Hot water inlet2: thermistor open or short circuit

Error Occurnace Conditions

This error is a sign of a problem with the hot water outlet 2 thermistor in your Navien tankless water heater. When sensor is open or shorted, this error accures.

Action

Check the thermistor and resistance value.
Replace the thermistor

Error Code E445 - Abnormal operation: Bypass mixing valve

Error Occurnace Conditions

If the mixing valve does not work properly due to a defective feedback sensor, mixing valve, or PCB board, the
system displays 445E (cleared automatically/manually).

– Mixing valve error – The system commands opening of the mixing valve, but the valve remains closed. [Check
the feedback sensor.] (Cleared manually)

– If a mixing valve sensor open or short-circuit is detected, the system displays an error message. If flow is
detected, the system clears the error automatically and provides hot water. If an open or short-circuit is
detected after hot water is used, the system displays the error message.

Action

If the 445 error occurs, connect the mixing valve to the PCB. The valve must be kept open when the water heater is not operating. If the PCB is defective, the motor keeps operating and the valve continually attempts to open or close the valve.

– Defective mixing valve
– Defective PCB
– Check the operation of the mixing valve using the Component Test mode.

Error Code E515 - Abnormal operation: PCB

Error Occurnace Conditions

If an error occurs in the internal circuit of the PCB (e.g., resistance, transistor or relay fault), the system displays 515E (cleared manually) on the PCB.

Action

Defective PCB
Check with a multimeter if the PCB is supplied with the proper voltage (AC 102~132 V).
Check the wire connection.
Disconnect the ground wire, then check the PCB.
Check if gas valve is properly connected to the wiring harness.

Error Code E517 - Abnormal DIP switch setting

Error Occurnace Conditions

Error E517 indicates that system has problem with the dip switch.

Action

Check the DIP switches on the front panel and PCB.
Replace the DIP Switch if necessary

Error Code E593 - Abnormal operation: front panel key

Error Occurnace Conditions

Problem with operation of the front panel keys trigger this error.

Action

Check if water is on the front panel keys.
Replace the front panel.

Error Code E594 - Abnormal operation: EEPROM

Error Occurnace Conditions

E594 in Navien indicates a partial PCB communication issue or an EEPROM problem.

Action

Check PCB for damage or wiring issues and replace the PCB if necessary.

Error Code E615 - Abnormal operation: input and memory

Error Occurnace Conditions

Error E615 indicates Abnormal signal input by PCB.

Action

Turn the POWER RESET switch OFF then ON (or unplug and replug the power supply.
If the system still displays E615, replace the main PCB.

Error Code E740 - Abnormal operation: outdoor temperature sensor

Error Occurnace Conditions

If an error (under 2.2kΩ or over 122.2kΩ) in the outdoor sensor is detected continuously for 3 seconds, The system displays the error message E740 on the front panel. If this occurs, the water heater changes the control mode from Reset Curve Mode to Normal Mode.

Action

Check if the outdoor sensor connector is wet due to any reason, including leakage.
Check the Resistance of the outdoor sensor.
Check the parameter setting.
Replace the defected Hot water outlet temperature sensor.
Replace the controller.

Error Code E760 - Flushing/service alarm

Error Occurnace Conditions

If the water heater operate more than set flushing time (day), The system displays the error message E760 on the front panel. If this occurs, the water heater operate with Normal Mode.

Action

Check the water heater and flushing the water heater, if it is required.
Reset the timer with reset button on the front panel.

Error Code E762 - Vent pipe not properly inserted

Error Occurnace Conditions

If the vent pipe of Navien tankless system is not inserted properly this error occures.

Action

Check if the vent pipes are properly installed.
Check if the vent switch operates properly.
Check if the vent switch’s connector is damaged.

Error Code E782 - Abnormal operation: main panel communication

Error Occurnace Conditions

Is the wiring from the front panel is not properly connected to the PCB this error occures.

Action

Check if the panel is connected to the PCB
If not, connect the it.
Reset the unit.
If problem persists, replace the PCB.

Error Code E785 - Abnormal operation: flow switch/sensor

Error Occurnace Conditions

If an AHU heating is OFF and Flow Rate is O and Flow Switch is detected continuously for 3 seconds, The Navien Tankless system displays the error message E785.

If this occurs, the water heater operate AHU heating Mode and operate DHW mode when the water heater detect saved flowrate plus 0.4gpm (1.5 lpm) more.

Action

Check if the Flow Switch is ON or OFF.
Check if flow switch is installed in the proper direction.
Check the Resistance of the terminal block.
Check if there is water flow and whether the switch is detecting flow.
Replace the controller.

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