Navien Error Codes, Code by Code

If your Navien tankless is showing a code like E003 or E110 and the hot water just quit, the display is telling you which part of the system stopped it. Some of those codes have a simple first check you can do yourself in a couple of minutes. Most of them don't, and knowing which is which saves you a wasted afternoon (and protects your warranty).

This is a code-by-code reference for Navien's NPE and NPE-2 condensing tankless water heaters, the units we see most in homes across Cabarrus, Rowan, and Iredell County. Every meaning below comes from Navien's own owner's manuals. For each code you'll get what it means, what's safe for a homeowner to check, and when it's time for a licensed tech.

First, Write Down the Code and Check Which Navien You Have

Before you press anything, write the code down or take a photo of the display. If you call us or Navien, that code is the first thing anyone will ask for.

Then find the model number on the rating label on the side of the unit. This matters because Navien's codes aren't universal across its whole product line:

• NPE-2 series (model numbers ending in A2 or S2, like NPE-240A2) and the original NPE series (ending in A or S) share almost the same code list. That's what this article covers.
• NPN, NHW, NCB combi-boilers, and NHB boilers each have their own manuals and their own code tables. A code that means one thing on an NPE can mean something different on a combi-boiler, so check the manual for your exact model if yours isn't an NPE.

Navien's NPE-2 owner's manual lists 32 error codes. For 21 of them, the only remedy it gives is to contact Navien Technical Support, which tells you how few of these are homeowner fixes.

How to Reset a Navien Tankless Water Heater

Navien's manuals say a reset can clear minor problems. On the original NPE, press the Reset button on the front panel. On the NPE-2, Navien's manual says to press the Back button to reset.

Reset once. If the same code comes back right away, or comes back every few days, the unit is telling you something real. Resetting it over and over won't fix the cause, and on codes tied to gas, venting, or overheating it isn't something to keep pushing through.

Navien Error Codes at a Glance

Codes not in this table (E031, E046, E047, E060, the E400-series sensor and valve codes, E517, E593, E594, E615, and the E700-series codes) all point to a technician in Navien's manual.

The Common Codes, One by One

E003: Ignition Failure

E003 means the unit tried to light the burner and couldn't. Navien's first instruction is simple: make sure the main gas supply valve is open.

What you can check: Look at the gas valve on the line going into the water heater and make sure the handle runs in line with the pipe (open). Check whether your other gas appliances, like the range or furnace, are working. If you're on propane, check the tank gauge. Then reset once.

When it's a tech call: If the gas is on and E003 comes back, the cause is past what a homeowner should chase. It can be gas supply that isn't reaching the burner properly, or ignition and flame-sensing parts that need service. Gas work and anything inside the cabinet is for a licensed plumber, and if you smell gas, leave the house and call your gas utility first.

E012: Flame Loss

E012 means the burner lit but the flame went out during operation. Navien's manual lists cleaning the air intake filter and checking that the electrical cord is properly grounded.

What you can check: Reset once and see if it holds. The intake air filter sits behind the front cover, and the grounding check is electrical, so we recommend leaving both to a tech.

When it's a tech call: If E012 repeats. A tech can clean the intake filter, check grounding, and look at the flame-sensing parts in one visit.

E016 and E030: Overheating (Heat Exchanger or Exhaust)

E016 means the heat exchanger is running too hot. E030 means the exhaust is: Navien's manual says the unit shuts down when the flue temperature passes 149°F. For both, Navien points to the same two fixes: clean the cold water inlet filter and flush the heat exchanger. On the original NPE, the manual also says to turn the system off for at least 30 minutes before restarting.

In plain terms, these usually mean water isn't moving through the heat exchanger the way it should, and the most common reason is scale or debris.

What you can check: The cold water inlet filter is a small screen where the cold line enters the bottom of the unit. Navien's manual covers cleaning it: power off, gas valve closed, water shut off at the inlet, drain the unit, then pull and rinse the screen. If you're comfortable with those steps, it's a reasonable homeowner task. If not, it's a quick part of any service visit.

When it's a tech call: If the screen is clean and the code returns, the heat exchanger likely needs a descaling flush. Navien's own manual calls the flush "a somewhat complicated procedure" and notes that improper maintenance can void your warranty. We cover what a proper flush involves in our Navien maintenance guide.

E109 and E110: Fan Motor and Air Pressure

E109 points to the fan motor. E110 means the unit sensed abnormal air pressure, which usually means it can't move air in or exhaust out the way it should. For E110, Navien says to make sure the exhaust pipe is free of obstructions and to clean the intake air filter.

What you can check: Go outside and look at where the vent and intake pipes leave the house. Clear away snow, leaves, or anything blocking the openings, without reaching into the pipe or taking anything apart. Navien's manual recommends checking the vent termination and air intake once a year anyway.

When it's a tech call: If the openings are clear and the code comes back, or if you see a vent pipe that's cracked, separated at a joint, or melted. Navien's manual says to turn the unit off and stop using it if the venting is damaged. Venting on a gas appliance is a carbon monoxide safety issue, and we go deeper on that in our tankless venting guide.

E438: Circulation Pump

E438 relates to the circulation pump, which runs the built-in recirculation on A and A2 models. On the original NPE, Navien says to make sure all water supply and return lines are open (for an external loop) or check the direction of the 2-way valve (for internal recirculation). On the NPE-2, the manual ties it to the pump when an air handler is installed and says to check that the pump is operating properly.

What you can check: If someone recently worked on your plumbing, make sure the valves on the hot, cold, and recirculation lines near the heater are fully open.

When it's a tech call: Anything past the valves. If you have a recirculation loop and want to understand how it's plumbed, our hot water recirculation guide explains the common setups.

E760: Flushing / Service Alarm

E760 isn't a failure. It's a maintenance reminder, and Navien's remedy is to have the installer perform routine service. If you see it, the unit is due for its flush and inspection.

E762, E773, and E788: Venting and Gas Type (NPE-2)

These are NPE-2 codes, and they're about safety, not comfort. E762 means the vent pipe isn't properly inserted into the unit's collar. E773 means the unit detected the wrong gas, and E788 means the gas type setting on the control doesn't match. All three are a tech call right away, and the unit shouldn't be run in the meantime.

Codes That Always Mean Calling a Tech

E004 (false flame detection), E031 (burner overheating), E046 and E047 (limit control and exhaust thermostat), E060 (dual venturi), the sensor and valve codes in the E400s (E407, E421, E432, E434, E439, E441, E445), the board and control codes (E515, E517, E593, E594, E615), the communication codes (E736, E782), and the outdoor sensor and flow switch codes used with an air handler (E740, E785) all involve internal parts or connected equipment. Navien's remedy for nearly all of them is to contact Technical Support, and the work happens inside the cabinet with power and gas involved.

For E004 and E515, the manual's first step is checking that the electrical cord is properly grounded. That's an electrical check, so leave it to a pro.

No Hot Water and No Error Code

This one sends a lot of people searching. If the hot water is off or runs cold and the display shows nothing, Navien's manual points to a few causes:

• The cold water inlet filter is clogged. Same screen as the E016 check above.
• Not enough flow to fire the burner. A tankless needs a minimum flow to turn on. Navien's manual says at least 0.5 gallons per minute, so a faucet barely cracked open may never get hot.
• The unit is frozen. More likely during a hard freeze, especially if the unit lost power.
• Cold water crossing into the hot line. Navien's manual says to check for cross plumbing between the cold and hot lines, and, if you have an external recirculation system, for a check valve on the return line.

On freezing: Navien's freeze protection needs electricity, so don't unplug the unit in winter. If the power or gas will be off for a long stretch, the unit should be drained. Navien doesn't cover freeze damage under its warranty.

Where DIY Stops

The line is pretty clear. A homeowner can safely:

• Write down the code and reset once
• Confirm the gas valve to the heater is open and the propane tank isn't empty
• Check that the unit has power
• Clear snow, leaves, or debris from the outside vent and intake openings, and check that the condensate drain line isn't kinked or frozen
• Clean the cold water inlet filter screen, if you're comfortable shutting off gas and water and draining the unit

Everything else goes to a licensed tech: gas line work, venting repairs, anything behind the front cover, and the heat exchanger flush if you're not set up for it. That isn't us protecting our work. Gas and venting are carbon monoxide and fire risks, and Navien's warranty requires a licensed installer and correct maintenance.

What About the Warranty?

Navien's warranty covers parts, labor, and the heat exchanger for set periods depending on how the unit is used, and it's tied to proper installation and maintenance by a licensed professional. Navien's manual says warranty service starts with the original installer, and that the tech should contact Navien Technical Support from in front of the unit before replacing parts.

So before you order a part online, call a licensed tech who knows Navien's warranty process. Our owner, Jonathan Johns, is a Navien Certified Service Specialist, and we handle that call with Navien as part of the visit.

How We Handle Navien Repairs

When you call Macaw with a Navien code, the person who diagnoses it is the person who does the work. Our owner, Jonathan Johns, is a Navien Certified Service Specialist, and we've repaired and maintained hundreds of tankless systems around Cabarrus, Rowan, and Iredell County.

We diagnose from the code and the unit itself, tell you what's wrong and what it'll cost before any work starts, and handle warranty coordination with Navien if your unit is covered. Our service call is $94, and it's waived when you move forward with the repair. After-hours visits are $189. Full water heater and tankless pricing is on our pricing page.

Frequently Asked Questions

What does error code E003 mean on a Navien tankless water heater?

E003 is an ignition failure: the unit tried to light the burner and couldn't. Navien's first step is to make sure the main gas supply valve is open. Check that the gas valve to the heater is on, that your other gas appliances work, and that a propane tank isn't empty, then reset once. If E003 comes back, call a licensed tech.

How do I reset my Navien tankless water heater?

On an original NPE, press the Reset button on the front panel. On an NPE-2 (model numbers ending in A2 or S2), Navien's manual says to press the Back button. Reset once. If the same code returns, the unit needs service.

Can I fix Navien error codes myself?

A few have a safe first check: E003 (gas valve open), E110 (outside vent and intake clear), and E016 or E030 (cold water inlet filter screen). Navien's NPE-2 manual lists 32 codes, and for 21 of them the only remedy is to contact Navien Technical Support. Gas, venting, and anything inside the cabinet belong to a licensed tech.

Why is my Navien not making hot water with no error code?

Navien's manual points to a clogged cold water inlet filter, too little flow to fire the burner (at least 0.5 gallons per minute), a frozen unit, or cold water crossing into the hot line. Start with the inlet filter and make sure the faucet is open far enough.

What does E760 mean on a Navien?

E760 is a flushing and service reminder, not a failure. Navien's remedy is to have the unit's routine maintenance done, which includes flushing the heat exchanger.

Do Navien error codes mean the same thing on every model?

No. The NPE and NPE-2 share nearly the same list, but NPN units, NHW units, NCB combi-boilers, and NHB boilers have their own manuals and code tables. Check your model number on the unit's rating label and use the manual for that model.

The codes in this article come straight from Navien's own NPE-2 User's Information Manual, which is worth keeping handy if you own one.

If your Navien is showing a code that keeps coming back, or you just don't want to guess, give us a call. We'll tell you straight what the code means on your unit and what it'll take to fix it. You can reach us at (704) 798-2659 or book online, and you can read more about our tankless water heater repair and maintenance service.