Navien tankless water heater error codes

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Navien tankless water heaters display error codes on the LED display panel to indicate a problem with the unit. Here are some of the most common Navien tankless water heater error codes:

Navien tankless water heater error codes

E001 Water is boiling in the Heat Exchanger 1. clean the inlet water straining 

2. Check the automatic flow

3. Check the heat exchanger, remove and clean with a solution

E003 Ignition Failure 1. Check to see if the main gas supply is on 

2. Check that the power is on

3. Check the igniter for spark

E004 False flame detection 1. Ensure ground wire is connected 

2. Check the igniter for spark

E007 Hot water outlet: thermistor -open 1. Check the thermistor 

2. Replace the thermistor

E008 Hot water outlet: thermistor -short 1. Check the thermistor 

2. Replace the thermistor

E009 Abnormal fan motor activity 1. Check and clean the air filter 

2. Check and clean the fan motor

E010 Abnormal Air Pressure 1. Check the vent pipe for obstructions 

2. Check and clean the air filter

E011 High Water Pressure 1. Check the water pressure sensor. 

2. Automatic Reset or replace sensor.

E012 Flame loss 1. Check the main gas line (valve open?) 

2. Check intake air pipe

3. Check the ground wire

4. Check power supply

E015 Abnormal control board 1. Check power supply 

2. Check the GFI

E016 Overheating of heat exchanger 1. Turn off the for at least 30 minutes then restart 

2. Clean the inlet water strainer

3. Check the automatic flow adjustment valve

4. Check the heat exchanger: remove and clean with a cleaning solution

E021 Cold water inlet: thermistor 1 -open 1. Check thermistor 

2. Replace thermistor

E022 Cold water inlet: thermistor 1 -short 1. Check thermistor 

2. Replace thermistor

E027 Abnormal activity of the air pressure sensor 1. Check the vent pipe for obstructions 

2. Check and clean the air filter

E028 Water leak pipe line 1. Check pipe line.
2. Replace O ring
3. Manual reset
E030 Exhaust overheat: exhaust high limit switch shuts down the unit when the flue temperature exceeds 230F or 110C for more than 10 minutes 1. Turn off the for at least 30 minutes then restart 

2. Clean the inlet water strainer

3. Check the water adjustment valve

4. Check the heat exchanger: remove and clean or flush system

E032 Cold water inlet: thermistor 2 -open 1. Check thermistor 

2. Replace thermistor

E033 Cold water inlet: thermistor 2 -short 1. Check thermistor 

2. Replace thermistor

E034 Abnormal – flow adjustment valve 1. Check the flow adjustment valve
E035 Abnormal activity of the gas pressure sensor 1. Check gas line
E036 Communication failure 1. Contact Navien Tech. support (800-519-8794)
E037 Water leak inside unit 1. Close cold water main 

2. Replace leaking parts

E038 Abnormal circulation pump 1. Check the circulation PUMP 

2. Check the water flow sensor

3. Check the cold water main

E039 Abnormal – water flow sensor 1. Check the water flow sensor
E041 Hot water outlet: thermistor 2 -open 1. Check thermistor 

2. Replace thermistor

E042 Hot water outlet: thermistor 2 -short 1. Check thermistor 

2. Replace thermistor

E043 Abnormal cascade connection 1. Check model type 

2. Check communication cable

3. Replace communication cable

E044 Abnormal thermistor connection 1. Check thermistor connection 

2. Replace thermistor

E045 Abnormal – mixing valve 1. Check the mixing valve 

2.Replace Mixing Valve

3.Check mixing valve transformer

E046 Abnormality in limit control Call technical support (800-519-8794)
E047 Abnormal exhaust thermistor 1. Check exhaust thermistor connection 

2. Call technical support (800-519-8794)

E048 Abnormal LPG gas pressure 1. Check the LPG gas 

2. Fill the LPG gas

3. Check gas pressure flow sensor

E060 Abnormal Operation: dual venturi 1. Check the dual venturi connection 

2. Replace dual venturi

3. Reboot System

E109 Abnormal fan motor activity 1. Check and clean intake air filter
2. Check and clean the fan motor
3. Replace fan motor
E110 Exhaust Blockage 1. Check the exhaust pipe for obstructions
2. Check and clean the intake air filter
E407 Hot water outlet 1: thermistor open or short 1. Check the thermistor
2. Replace the Thermistor
E421 Cold water inlet 1: thermistor open or short 1. Check the thermistor
2. Replace the Thermistor
E432 Cold water inlet 2: thermistor open or short 1. Check the thermistor
2. Replace the Thermistor
E434 Abnormal Operation: Water adjustment valve 1. Check adjustment valve.
2. Replace valve
3. Contact Technician
E438 Abnormal Operation: circulation pump 1. External: Ensure all water lines are open
2. Internal: Check two way valve direction
E439 Abnormal Operation: flow sensor 1. Contact Technician
(800-519-8794)
E441 Hot water inlet 2: thermistor open short circuit 1. Call technical support (800-519-8794)
E445 Abnormal Operation: Bypass Mixing valve 1. Call technical support (800-519-8794)
E515 Abnormal Operation: PCB 1. Ensure electrical cord is properly grounded 

2. Try new outlet

E517 Abnormal Operation: Dip switch setting 1. Call technical support (800-519-8794)
E593 Abnormal Operation: Front Panel Key 1. Call technical support (800-519-8794)
E615 Abnormal Operation: input and memory 1. Call technical support (800-519-8794)
E736 Abnormal Operation: Cascade communication 1. Call technical support (800-519-8794)
E760 Flushing Service Alarm 1. Call for system flush 

2. Purchase flush kit and do it yourself.

E782 Abnormal Operation: Main panel Communication 1. Call technical support (800-519-8794)

There will be error codes on both the remote control and on the computer board on the main unit.

 

  • E001 – Water is boiling in the Heat Exchanger. This may be due to a clogged inlet water strainer, a faulty automatic flow sensor, or a problem with the heat exchanger itself.
  • E011 – Water pressure is too low. This may be due to a problem with the water supply, a faulty water pressure sensor, or a problem with the water pump.
  • E021 – Water temperature is too high. This may be due to a problem with the thermostat, a faulty temperature sensor, or a problem with the burner.
  • E031 – Gas valve is not opening. This may be due to a problem with the gas valve itself, a faulty gas pressure regulator, or a problem with the electrical wiring.
  • E041 – Fan is not running. This may be due to a faulty fan motor, a problem with the electrical wiring, or a blockage in the exhaust vent.

If you see one of these error codes on your Navien tankless water heater, you can try the following to resolve it:

  • Check the inlet water strainer. If it is clogged, clean it with a brush or a pipe cleaner.
  • Check the automatic flow sensor. Make sure that it is properly connected and that the wires are not damaged.
  • Check the heat exchanger. If it is damaged, it will need to be replaced.
  • Check the water pressure. It should be between 30 and 80 psi. If it is lower than 30 psi, you will need to increase the water pressure to the unit.
  • Check the temperature sensor. Make sure that it is properly connected and that the wires are not damaged.
  • Check the thermostat. Make sure that it is set to the correct temperature.
  • Check the gas valve. Make sure that it is properly connected and that the wires are not damaged.
  • Check the gas pressure regulator. Make sure that it is properly adjusted.
  • Check the electrical wiring. Make sure that there are no loose or damaged wires.
  • Check the exhaust vent. Make sure that it is clear of blockages.

If you have tried all of the above and you are still seeing the error code, you will need to contact a qualified technician to diagnose and repair the problem.

Here are some additional tips for troubleshooting Navien tankless water heater error codes:

  • Consult the owner’s manual. The owner’s manual will provide more detailed information about the error codes and how to troubleshoot them.
  • Check the Navien website. The Navien website has a troubleshooting section that can be helpful in resolving error codes.
  • Contact Navien customer support. Navien customer support can provide assistance in troubleshooting error codes and scheduling a service call.

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