Navien Water Heater Fault Codes
Every documented Navien tankless and combi water heater error code, what it means, and when it needs a professional.
Navien built its reputation on condensing tankless technology, and the NPE, NCB, and NHB lines that resulted are some of the most common residential tankless and combi (tankless-plus-hydronic-heat) units installed in North America. This page covers the fault codes documented for those series — what each one tells the control board detected, what typically causes it, what a homeowner can safely check, and where the job hands off to a licensed plumber or HVAC technician.
How to read a Navien fault code
Navien doesn't make you count LED blinks the way some manufacturers' basic tank models do. The wired remote controller (or the built-in control panel on models without a separate remote) has an LCD that normally shows the set temperature, and when the unit detects a fault it replaces or overlays that display with a direct alphanumeric code — something like E003 — instead of a flash pattern you have to time and tally. If you've paired the unit with the NaviLink Wi-Fi app, the same code typically shows there too. Either way, the code itself is the starting point: look up the exact letters and digits below rather than guessing from symptoms alone, since two different Navien faults can produce very similar symptoms (no hot water, short-cycling) with completely different root causes.
All Navien codes
| Code | What it means |
|---|---|
| E003 | Ignition Failure — the unit couldn't light the burner |
| E004 | False Flame Detection — board senses flame that isn't there |
| E110 | Exhaust Blockage — vent obstruction, very common in winter |
| E016 | Heat Exchanger Overheating — unsafe temperature detected |
| E012 | Flame Loss — burner lit, then the flame dropped out |
| E060 | Dual Venturi Limit Switch Error — NPE air-intake switch fault |
| E205 | H/E Outlet Error — outlet temperature sensor open or shorted |
| E302 | Low Water Pressure Error — incoming pressure below minimum |
| E439 | Abnormal Flow Sensor — flow sensor or activation fault |
| E515 | PCB Error — main control board fault |
No code showing, just a symptom?
If the display is blank, unreadable, or you haven't located it yet, it's often faster to start from what the water heater is actually doing: no hot water from a tankless unit, ignition failure, the cold water sandwich effect, water that's not hot enough, or a code that's flashing but hard to read. Each of those symptom pages links back to the specific codes most likely to be behind it.
Independent, not affiliated
This page is not affiliated with, endorsed by, or sponsored by Navien. "Navien," "NPE," "NCB," and "NHB" are used only to identify which products a given code applies to. Read the full methodology.