Navien tankless water heaters are an efficient alternative to traditional tank-style water heaters. They heat water on demand, rather than keeping a tank of water hot 24/7. This eliminates standby heat losses and can reduce energy costs. 

Navien units have a digital display screen that shows information like temperature settings and flow rate. If there is an issue, the screen will start flashing red and show an error code. This helps identify problems before they become major. 

This article will go over some of the most common reasons why a Navien’s screen may start flashing red. We’ll explore error codes related to overheating, flame failure, low water flow, ignition failure, sensors, and more. Understanding these codes can help determine whether it’s a DIY fix or time to contact a professional.  

Reasons for Flashing Red Screen

Seeing a flashing red screen on your Navien tankless water heater can be concerning, but it’s the unit’s way of alerting you to an issue that needs attention. There are several common reasons why the screen may flash red: 

Overheating Protection Triggered

Navien Tankless Water Heater Overheating Problem

Tankless water heaters have built-in overheating protection that is triggered if the unit exceeds a safe temperature threshold. This often happens if the heat exchanger is blocked or the water flow is too low. The flashing red light indicates the unit has powered down to prevent damage. 

Navien heaters have a high limit switch that will shut off the burner if the internal temperature exceeds 190°F. This safety mechanism prevents dangerous overheating. There are several potential causes for overheating: 

  • Restricted airflow  
  • Scale buildup  
  • Pump issues  
  • Bad burners  

If overheating is the cause of the error, addressing the underlying issue like restricted airflow, scale buildup, plumbing problems, or burner maintenance will stop the red screen flashing. 

Flame Failure

The flame rod is a metal probe that sits in the burner assembly. It conducts electricity when heated by the flame during normal operation. If the rod does not sense a flame, it cannot conduct electricity back to the control board. This triggers the error code and flashing red screen.  

If the system failed to ignite or detect a flame, this could mean the gas supply was interrupted, a strong draft blew out the flame, or there is an issue with the igniter or flame sensor. A flashing red light alerts you to relight the pilot or address the underlying problem. 

If the Navien water heater continues to show flame failure codes, inspection and cleaning of the flame rod is a good first step. But other gas valve or ignition problems may require a professional service call. Persistent flame failures can indicate a serious issue that should not be ignored. 

Low Water Flow/Pressure

Tankless heaters need a minimum water flow rate to operate properly. If the water pressure drops too low, it will trigger the flashing red light. Increasing flow at fixtures can resolve this. 

Navien tankless water heaters have flow sensors that monitor the rate of water flow through the unit. These flow sensors allow the heater to modulate its burner output to match the hot water demand. 

If the flow rate drops too low, it means there is insufficient water volume moving through the heat exchanger. This can lead to overheating and trigger the error code. There are a few potential reasons for low flow: 

  • Closed water supply valves 
  • Pump problems  
  • Clogged water filters  
  • Scale buildup  

If low flow is detected, the first step is confirming valves are open, the pump works, and filters are clean. If water pressure and volume are adequate, the unit may need professional service to address other issues like scaling. 

Ignition Failure

The Navien tankless water heater goes through an ignition sequence to light the burner each time hot water is called for. This involves the gas valve opening to allow fuel to flow, and the ignition control module creating a spark to light the burner. 

If the burner fails to ignite, it’s usually due to an issue with one part of this ignition system. Some common causes include: 

  • Faulty igniter or ignition control module  
  • Gas valve problem 
  • Insufficient gas flow  
  • Wiring issues  

If the Navien unit is flashing an ignition error code, it requires diagnosis and repair to get the ignition sequence working properly again. This often involves a technician testing components like the igniter, gas valve, and wiring for faults. 

Sensor Issues

Faulty temperature sensors, water flow sensors, or other detection sensors can prevent normal operation and show error codes. A technician can troubleshoot and replace any problematic parts. 

The Navien tankless water heater relies on sensors to monitor operations and detect issues. Some common sensors include: 

Water Flow Sensor – Detects the flow rate of water through the unit. If the flow rate drops too low, it will shut off the burner to prevent overheating. A bad flow sensor can cause error codes related to low water flow. 

Flame Rod Sensor – Detects whether a flame is present from the burner. If no flame is detected, it will shut off gas to the burner. A faulty flame rod can cause ignition failure errors. 

Temperature Sensors – Measures the temperature at various points, like the inlet and outlet pipes. This helps regulate water temperature. Faulty temp sensors can cause overheating errors. 

If error codes point to a sensor, they may need cleaning or replacement. Always turn off power and gas to the unit before working on sensors. Consult manufacturer instructions to locate and safely access sensors for troubleshooting. 

Exhaust or Combustion Air Issues

Navien tankless water heater Exhaust Problem

Tankless water heaters require proper exhaust and air intake to function safely and efficiently. If there are problems with the exhaust or combustion air, it can trigger the flashing red error screen. 

Common causes of exhaust or combustion air issues include: 

  • Restrictions or blockages in the exhaust vent pipe.  
  • Leaks in the exhaust venting.  
  • Improper vent length or diameter.  
  • Recirculation of exhaust gases.  
  • Lack of combustion air.  

If exhaust or combustion air issues are suspected, inspection by a professional is recommended to identify and resolve the problem. Proper venting is critical for safe operation. 

Interpreting Error Codes

When the Navien water heater has an issue, it will display an error code on the front panel. The code gives you an indication of what the problem may be. To fully interpret the code, you’ll need to check the meaning in your owner’s manual. 

For example, code “A2” on a Navien tankless water heater indicates an overheating issue. This means the unit shut down because it exceeded the max allowed internal temperature as a safety precaution. 

Another common code is “C2” which signals a flame failure. This means the burner failed to ignite or the flame was unstable and went out during operation. The system will try to relight a certain number of times before giving up and showing this error. 

When you see an unfamiliar code, don’t panic. Simply look it up in your manual to understand the issue. The code will guide you or a technician toward the correct troubleshooting steps. 

When to Call a Professional

Technician Working on a Water Heater

Even with a good understanding of error codes and troubleshooting steps, there are times when it’s best to call in a professional for Navien tankless water heater repairs and maintenance. 

For complex repairs beyond basic troubleshooting

If you’ve worked through all the basic troubleshooting steps and your Navien heater is still not working properly, it’s time to call a professional. There could be complex electrical, gas line, or mechanical issues that require specialized expertise to diagnose and repair. Don’t continue guessing at the problem if you’ve exhausted your DIY troubleshooting abilities. 

If safety/gas work is required

Any repairs involving the gas lines, gas valve, burners or other gas components should only be done by qualified professionals. Gas work can be extremely dangerous if not done properly, so don’t take risks doing it yourself. Licensed professionals have the proper training and experience. 

For annual maintenance

While you can do some basic maintenance yourself, it’s recommended to have a professional service your Navien once a year. They will check all systems, clean parts, test for gas leaks, inspect exhaust venting, and perform other important maintenance tasks. This helps keep your heater running safely and efficiently. 

If you are having issues with a Navien tankless water heater installed by Provincial Smart Home Services, contact one of our expert energy advisors and they will help you schedule a service call. Additionally, you can download our new customer service app on the Apple Store or Google Play Store for additional resources that can help you resolve any issues you might encounter with your unit.    

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