Navien Error Codes: What Each E Code Means and What to Check

A Navien error code is a three-digit number that starts with E, such as E003 or E012, shown on the front panel when the water heater stops or limits itself to protect against a fault. Press the Back button once to reset it. If the code comes straight back, look it up in the table below: a few codes have owner checks, such as opening the gas valve or cleaning a filter, and the rest need a licensed technician or Navien support.

How to read and clear a Navien error code

On the NPE-A2 and NPE-S2 tankless water heaters, the error shows on the front panel display. Navien's NPE-2 user's information manual labels one area of that display "Combustion/Error", which shows whether the burner is firing or a fault has been found. Write the code down before you do anything else, because a reset clears it from the screen.

To reset, press the Back button on the front panel. The manual says a reset may fix minor problems, and that the water heater keeps your settings during a power outage. If the reset does not solve it, Navien's next step is the troubleshooting chart, then an authorized technician, a licensed professional or Navien Technical Support at 1-800-519-8794.

On the optional remote and the NaviLink app

The NR-21DU remote controller, listed on Navien's NPE-A2 downloads page, shows a flashing red LED and an error icon next to the three-digit code. Its remote controller manual says to fix the cause first, then press OK once. "RST" appears on the screen when the error resets.

NaviLink is Navien's add-on Wi-Fi control. Navien's NaviLink page lists "error code notification / status" for the NPE-A2, NPE-S2 and NCB-H series, and push notifications for diagnostic error codes on the NCB-H combi. The page does not explain how the code looks in the app, so read the number and match it to the table below.

Navien NPE error code table

These are every code in section 5.2 of the NPE-2 user's information manual (models NPE-180A2, NPE-210A2, NPE-240A2, NPE-180S2, NPE-210S2 and NPE-240S2), as of October 2026. The checks column holds only what that manual tells the owner to do.

If a code is not in this table, or a check does not clear it, Navien's manual ends the chart with one instruction: contact Technical Support at 1-800-519-8794.

E003: ignition failure

E003 means the burner did not light. Navien gives the owner one check: make sure the main gas supply valve is open. It is the same gas valve the manual tells you to close before draining the unit.

1. Check that the gas valve to the water heater is open.
2. Check that other gas appliances in the house work, which tells you gas is reaching the home.
3. Press the Back button to reset, then open a hot tap.
4. If E003 comes back, stop and call a technician or Navien support.

Step 2 is our suggestion, not Navien's. If you smell gas, do not reset anything. Navien's manual says not to touch electrical switches or use a phone in the building, and to call your gas supplier from a neighbor's phone. Leave the house first. Navien also notes that this water heater has no pilot and lights itself, so never try to light the burner by hand.

E012: flame loss

E012 means the burner lit and then went out. Navien's two checks are cleaning the intake air filter and making sure the power cord is properly grounded.

The air intake filter sits at the top left of the water heater, behind the front cover. The manual's steps:

1. Press the Power button to turn the water heater off, then disconnect the power supply.
2. Remove the front cover and the screw that holds the air intake filter.
3. Pull the filter out, remove it from its plastic assembly, and clean it with a toothbrush and clean running water.
4. Let it dry completely, refit it, secure it with the screw and replace the cover.
5. Reconnect the power and press the Power button.

Navien says to clean this filter every 3 to 4 months, because a filter clogged with dust or lint stops the water heater and brings up E110. If you are not sure the outlet the water heater plugs into is grounded, have an electrician check it rather than guessing.

E016 and E030: overheating

E016 is heat exchanger overheating. E030 is exhaust overheating: the manual says the water heater shuts down when the flue temperature passes 149 °F (65 °C). Navien gives both codes the same two remedies, cleaning the cold water inlet filter and flushing the heat exchanger.

Clean the cold water inlet filter

You drain the unit first. Per the manual: put a bucket under the water heater, press Power to turn it off, close the gas valve, close the cold water supply valve to the water heater (or the water main if there is none), and open the hot taps to drain the lines. Then remove the cold water inlet filter (and on A2 models, the recirculation inlet filter), rinse it under cold running water, scrub it with a brush if needed, refit it and tighten it. Reverse the steps to refill.

Flush the heat exchanger

Navien calls flushing "a somewhat complicated procedure." It needs a 5-gallon bucket, cleaning solution diluted with water, three hoses and a circulation pump hooked to the service valves on the water lines, and the solution runs through the unit for at least 45 minutes. The manual warns that improper maintenance can void your warranty and says to call an authorized technician if you are unsure of any step. Our tankless water heater reset guide covers what to try before you get to this point.

E110 and E109: air and fan codes

E110 is abnormal air pressure. Navien says to make sure the exhaust pipe is free of obstructions and to clean the intake air filter (steps above). You can look at where the vent leaves the house, but do not take vent pipes apart yourself. E109 is a fan motor fault, and Navien's only owner step is cleaning the intake air filter.

E760: the flushing or service reminder

E760 is not a breakdown. Navien lists it as a flushing or service alarm and says to contact your installer to perform routine service. The NR-21DU remote manual also describes a scale warning that comes on when the water heater needs cleaning. Holding OK for 2 seconds turns that alarm off, but it does not do the cleaning, so book the service.

Navien combi boiler (NCB-H) codes are not the same

The NCB-H combi boilers use the same E-number format, and many numbers overlap, but the NCB-H user's information manual (dated March 2024, models NCB-190/060H to NCB-250/150H) has its own table. Some shared numbers mean something else or carry a different owner step:

If you own a combi, use the NCB-H manual's table, not the one above. Both manuals give the same reset: press the Back button.

Which Navien models this page covers

The main table comes from the NPE-2 user's information manual, which covers the condensing NPE-A2 and NPE-S2 tankless water heaters in the 180, 210 and 240 sizes. We checked the newer NPE-A2/S2 installation manual (January 2026) as well; it does not carry its own code chart and sends owners to the user's manual for troubleshooting. Other Navien lines, such as the NPN non-condensing models, have their own manuals, which we have not checked for this page. Find your model number on the unit's rating label and match it to your own manual before acting on a code.

For problems that show no code at all, such as lukewarm water or slow hot water, see our list of common water heater problems. If you also own a Rinnai, our Rinnai error codes page covers that brand.