Navien NPE-2 Code E110
Abnormal air pressure. The heater is not seeing the airflow it expects through the combustion and vent path. Navien's two owner remedies are to make sure the exhaust pipe is free of obstructions and to clean the intake air filter.
Call a proThe verdict
Call a licensed plumber
Both of Navien's remedies are free and worth doing: look at the vent terminal outside, and clean the intake air filter. What you should not do is take vent pipe apart or run the unit with the vent disturbed — a blocked or badly assembled vent recirculates exhaust gas.
Typical cost: $0–$900
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the NPE-2 — not averaged across the brand.
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Go outside and check the vent terminal for snow, leaves, a nest, or a dryer vent blowing into it.
- Clean the intake air filter.
- Do not disconnect or disassemble any vent section yourself.
- If the code survives both checks, book a licensed professional.
Frequently asked questions
Is E110 dangerous?
The heater stopping is the safe outcome — it refuses to burn without the airflow it expects. What is not safe is running it with the vent disturbed or resetting repeatedly past a real blockage.
It only happens in winter.
Then look at snow and ice first, at the vent terminal and around it. A terminal that drifts over, or a condensate line that freezes, produces this code and clears itself when things thaw — which is why it seems to come and go.
Code E110 on other Navien series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: