navien e351 error code

A Navien water heater can stop working and show an error code 351, you get Navien E351 Error Code if the water level is low. Normally, these systems will automatically refill themselves. However, in some cases, the 351 error could be caused by a frozen auto feeder valve, a closed cold water valve, or a malfunctioning thermostat. Additionally, the thermistor in a Navien water heater may be damaged, and it’s necessary to contact a licensed contractor to repair or replace it.


How to fix Navien E351 Error Code

The Navien E351 Error Code indicates that the water heater is not receiving enough water flow. This can be caused by a number of factors, including a blockage in the water line or a problem with the water pressure. To fix the issue, first check to see if there is a blockage in the water line. If there is, you’ll need to clear it before proceeding. If the water line is clear, then you’ll need to adjust the water pressure. The most likely cause of the Navien E351 Error Code is a problem with the water pressure. If you can’t fix the issue yourself, then you’ll need to call a plumber.

Check the gas supply pressure

The error code E351 on a Navien furnace can mean one of several things. Either there is a problem with the gas supply pressure or the main gas valve.


How to fix: If the former is the case, you can check the gas supply pressure by checking the gas supply pressure valve. If neither of these is the issue, you may need to check the air filter or power supply.

When the pressure drops below the normal operating pressure, the flame and sound are the results. A faulty gas orifice plate could also be to blame.

How to fix: Make sure there is no debris in the gas inlet pipe or on the gas orifice plate. Check the pressures on these components to ensure that you are running at full capacity.

If the error code E351 continues, you should call a licensed professional to perform a repair. They will have more expertise in Navien tankless water heaters and will be able to provide the necessary parts. If you do decide to replace the Navien tankless water heater yourself, check the PCB board first. If the board is faulty, it needs to be replaced. The replacement part must match your model. Once the PCB board is replaced, the machine will reset itself.

The 351 error code can be troublesome for many reasons. The main reason for this is that the pressure in the heating system drops too much. This happens during winter, and you should ensure that the gas supply pressure is at least 3.5″ w.C. If the pressure is too low, you should also check the auto feeder valve. If the auto feeder valve does not close properly, it may have a faulty water pressure sensor.

Check the outdoor temperature sensor

When you receive a Navien e351 error code, the most likely cause is a malfunction with the outdoor temperature sensor. Ensure the sensor’s wiring is properly connected. Also, make sure the outdoor reset curve is enabled, and that it is properly configured.

If you are unable to resolve this problem, you may need to contact a licensed professional to perform the necessary repairs. These professionals have specialized knowledge of tankless water heaters and can easily get the proper parts to repair the issue. If you are unable to locate the problem on your own, check the PCB board to determine the cause. If the board is faulty, it will need to be replaced. When replacing the board, make sure to buy a compatible replacement. If the problem persists, you may have a leak in your tank or another problem with the heat exchanger.

If you are unable to identify the exact cause of the Navien e351 error code, you can attempt to diagnose the problem by following some simple steps. For starters, you must check the outdoor temperature sensor. If this is working properly, the error should not appear again. If the outdoor temperature sensor is damaged or not connected properly, you may need to replace it. If that does not solve the problem, you may need to replace the main gas valve. In addition, you should also check the wiring at the heat exchanger.

Check the PCB (circuit board)

If your Navien water heater is showing an E351 error code, there are several ways to troubleshoot the problem. First, make sure the water pressure sensor or auto feeder valve is not faulty. If you cannot determine whether these components are malfunctioning, it is best to call a Navien technician to inspect the unit.

If you still can’t fix the error, you should check the PCB. If it is not in good condition, you should replace it. This is because Navien error codes can also indicate problems with the thermistor or a connection. In some cases, the problem could be a simple problem with the heat exchanger itself.

The faulty PCB may be causing a series of problems, including flame loss or noise. Another common cause is a malfunctioning gas orifice plate. A faulty gas inlet pipe could be causing this problem as well. If these problems are caused by the PCB, then it may be time to replace the unit. If this doesn’t solve the problem, you can consult your Navien manual to learn more about fixing the unit.

If you suspect a problem with the PCB of your Navien water heater, check its components for any broken wiring. Also, check the high-limit switch and the exhaust sensor to make sure they’re working properly. If this still doesn’t help, you should try cleaning the strainer.

Check the cascade communication

If you have a Navien tankless water heater, you’ll need to check the cascade communication for this error code. This error indicates a problem with the temperature sensor, external flow switch, or PCB. If you are unsure of what’s causing the error, consult a technician to determine the cause and correct it.

The NMB service manual has an error code list that you can refer to. For example, the e439 error code means that one or more units in the cascade system have a faulty flow sensor. If this sensor is causing this error, you will be able to see the error on the front panel.


If you have a Navien tankless water heater, you may have come across the E351 error code. This code indicates that there is a problem with the heat exchanger and needs to be addressed as soon as possible. In this blog post, we will explore what the E351 error code means and how you can fix it. We will also provide some troubleshooting tips in case you run into this problem again in the future.

Navien E351 Error Code FAQ

What is the Navien E351 Error Code?

The Navien E351 Error Code indicates that there is a problem with the water heater’s gas valve. This error code can be caused by a number of different things, including a faulty gas valve, a clogged vent pipe, or a problem with the electrical connection to the gas valve. If you see this error code, it is important to call a qualified technician to diagnose and repair the problem.

Causes of the Navien E351 Error Code

There are a few different causes for the Navien E351 Error Code. One common cause is a problem with the heat exchanger. Another possible cause is an issue with the condensing fan motor. Additionally, the error code can be caused by a problem with the main board or by debris in the system.

How to Fix the Navien E351 Error Code

If your Navien E351 Error Code appears, it means that there is a problem with the water pressure in your home. The first thing you should do is check the pressure gauge on your water heater. If it’s reading low, you’ll need to increase the water pressure in your home. This can be done by opening the main water supply valve all the way.

If the pressure gauge is reading normal, but you’re still getting the E351 Error Code, it’s likely that there’s a problem with the PRV (pressure relief valve). To fix this, you’ll need to open up the PRV and clean out any debris or sediment that may have built up inside. Once you’ve done that, close the PRV and restart your Navien unit.

If you’re still seeing the E351 Error Code after following these steps, there may be a more serious problem with your Navien unit. In this case, it’s best to contact a certified technician for further diagnosis and repairs.