E110
Navien Tankless Water Heater
Severity: ModerateWhat it means
Navien E110 is an abnormal air-pressure fault — the unit ran its pre-fire airflow check and the result was outside what it allows, so it won't light the burner.
The everyday cause is a blocked vent or intake termination: a nest, a screen iced over, lint from a nearby dryer vent.
It also shows up when the vent run is too long or has too many elbows for the model, or when the combustion fan is getting weak.
You get cold water until the air path is sorted.
Affected Models
- Navien NPE-180A, NPE-210A, NPE-240A (Classic)
- Navien NPE-180S, NPE-210S, NPE-240S
- Navien NPE-2 series
- Navien NCB-E combi-boilers
- Navien NPN series
Common Causes
- Vent or intake termination blocked — bird/wasp nest, leaves, lint, snow, ice
- Vent run longer or with more elbows than the model's limit
- Intake and exhaust terminations placed too close together (recirculating exhaust)
- Combustion fan running slow from dust or a worn bearing
- Sagging vent pipe holding a slug of condensate
- Air pressure sensor or its hose faulty (overlaps with E060)
How to Fix It
-
Go look at the terminations.
This fixes most E110s.
Find the intake and exhaust pipes outside.
Clear nests, leaves, lint, snow, or ice from the openings and screens.
If a dryer vent or another exhaust is right next to them dumping lint, that's worth fixing too. -
Reset and test.
Power off at the panel, ten seconds, power back on, run a hot tap.
If you cleared a blockage, E110 should be gone.
If it comes back with the terminations clearly open, the problem is the vent design or the fan. -
Check the vent length and layout.
Navien publishes a maximum equivalent vent length per model (each elbow counts as several feet).
If your install pushes past it — or the intake and exhaust caps are mounted closer together than the manual allows — the airflow check will keep failing.
That's an installation fix: shorten the run, upsize the pipe, or move a termination. -
Inspect the pipe for sags.
Condensing vents should slope back toward the unit so condensate drains; a sag traps water and chokes airflow.
Re-support any drooping section so it runs at a steady pitch with no low spots. -
Check the combustion fan.
Breaker off — flick the fan wheel.
It should spin freely and quietly.
Dust-caked wheel: vacuum it.
Grinding bearing: the fan motor needs replacing, and that's usually a tech job. -
Still failing? It's the fan or the pressure sensor.
Terminations clear, vent within spec, no sags, fan spins clean — then the combustion fan is underperforming or the air pressure sensor is bad.
Call Navien service to test and replace.
Frequently Asked Questions
E110 keeps coming back every winter — why?
Frost and snow at the vent termination.
Condensing tankless units put out a visible plume of moist exhaust, and in cold weather that can build frost on the screen and around the cap — especially on low sidewall terminations near the ground.
Brushing it clear gets you running again, and raising the termination or fitting a manufacturer-approved cold-climate vent kit stops it recurring.