Navien error code E012: flame loss

By Jason Dearmin · Last reviewed November 14, 2026 · How we check facts

What E012 means

Each Navien User's Information Manual has a section 5.2, "Understanding Error Codes", with a reason and a self-diagnostic action for every code. E012 is Flame loss in all four manuals we read. Navien lists ignition failure separately as E003, so E012 is the code for a flame that was lost, not a burner that never lit.

What each Navien manual says

So whichever Navien you own, the first two checks are the same. None of the four manuals tells owners to open the gas system, adjust the burner or change settings inside the unit.

Why the intake air filter comes first

The NPE-2 manual (section 4.5) explains that if the air intake filter becomes clogged by dust or lint, the water heater will stop operating and show a code on the display (it names Error Code 110 there). It asks owners to clean the air intake filter every 3 to 4 months. Navien also puts the same filter first in its E012 actions. If the heater sits in a dusty or linty space, such as near a clothes dryer, check the filter more often.

Navien's filter cleaning steps (NPE-2 manual)

1. Press the Power button on the front panel to turn the water heater off.
2. Disconnect the power supply to the water heater.
3. Remove the front cover.
4. Remove the screw that secures the air intake filter (on the NPE-2 it is at the top left of the water heater) and pull the filter out.
5. Remove the filter from its plastic assembly and clean it with a toothbrush and clean running water.
6. Let the filter dry completely, then reinsert it, put the assembly back and secure it with the screw.
7. Replace the front cover, reconnect the power supply and press Power to turn the heater back on.

Filter location differs between models, so follow the maintenance section in your own manual. If you are not comfortable removing the front cover, this is a quick job for the installer during a service visit.

The grounding check

All four manuals say to ensure the electrical cord is properly grounded. For a homeowner that means: the unit is plugged into a working three-prong grounded outlet, with no two-prong adapter, and the plug is fully seated. Navien gives the same grounding action for E004 (false flame detection) and E515 (PCB). Testing the outlet ground or the house wiring is a job for an electrician.

Gas type setting (NPN models)

The NPN manual adds a check that the gas manifold and fuel DIP switch setting match the supplied gas type, natural gas or propane. This matters mostly after a new installation or a fuel conversion. Changing the manifold or DIP switches is installer work; as an owner, just confirm which fuel your home uses and tell the technician.

Resetting and when to call

The NPE-2 manual says that for minor problems, resetting may resolve the issue, and that you reset by pressing the Back button on the front panel. If resetting and the suggested remedies do not resolve the problem, Navien says to contact an authorized technician, a licensed professional, or Navien Technical Support at 1-800-519-8794. Reset once after doing the checks, not over and over.

Safe homeowner checks for Navien E012

1. Note the code and modelWrite down E012 and the model number from the rating label, then turn the unit off with the Power button.
2. Clean the intake air filterDisconnect power and clean the air intake filter following the maintenance section of your Navien manual. Let it dry completely before reinstalling.
3. Check the plug and outletMake sure the unit is plugged fully into a grounded three-prong outlet with no adapter.
4. Reset onceReconnect power, turn the unit on and reset from the front panel. If E012 returns, call an authorized technician or Navien Technical Support.

Frequently asked questions

Is E012 the same on a Navien combi-boiler?

Yes for the NCB-H. Its manual lists E012 as Flame Loss with the same two actions: clean the intake air filter and ensure the electrical cord is properly grounded.

What is the difference between E003 and E012?

Navien lists E003 as ignition failure and E012 as flame loss. For E003 the manuals point first at the gas supply valve; for E012 they point first at the intake air filter and grounding.

How often should I clean the Navien air intake filter?

The NPE-2 manual says every 3 to 4 months. Dusty locations may need it more often.

Should I unplug the heater in winter while I wait for a technician?

Only to do the filter cleaning. The NPN manual warns that freeze protection needs electricity, so do not leave a unit in a cold space unplugged.

Sources

• User's Information Manual: NPE-2 Condensing Water Heaters (NPE-180/210/240A2 and S2), section 5.2 Understanding Error Codes (Navien) Covers: Navien NPE-180A2, NPE-210A2, NPE-240A2, NPE-180S2, NPE-210S2 and NPE-240S2 condensing tankless water heaters.
• User's Information Manual: NPE Condensing Water Heaters (NPE-180/210/240A and NPE-150/180/210/240S), section 5.2 Understanding Error Codes (Navien) Covers: Navien first-generation NPE-A and NPE-S condensing tankless water heaters.
• User's Information Manual: NPN Non-Condensing Water Heaters, section 5.2 Understanding Error Codes (Navien) Covers: Navien NPN-series non-condensing tankless water heaters (NPN-120E through NPN-199U). Condensing NPE/NCB models have their own manuals.
• User's Information Manual: NCB-H Condensing Combi-Boilers, section 5.2 Understanding Error Codes (Navien) Covers: Navien NCB-190/060H, NCB-190/080H, NCB-240/110H, NCB-240/130H and NCB-250/150H combi-boilers.

Safety note: this page is general information drawn from the sources above. Gas, combustion and line-voltage repairs belong to a licensed professional. Your own equipment's label and manual take priority over anything here. Read the full disclaimer.