Navien tankless water heater code E110
Abnormal air pressure. Code E110 means the same thing on all 2 Navien series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code E110 means on each Navien series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| NPE-2 | Abnormal air pressure | Call a pro | $0–$900 |
| NPE-A / NPE-S | Abnormal air pressure | Call a pro | $0–$900 |
Each row opens the full page for that generation. We hold manuals for NPE-2 and NPE-A / NPE-S, and each one gets its own reading of code E110 — what Navien documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 2 series in four columns, which is enough to route you and not enough to explain anything. This is the Navien wording behind each row, one entry per manual, so you can see where the 2 readings of code E110 agree and where they part company.
NPE-2 — 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.
NPE-A / NPE-S — Abnormal air pressure
The unit is not seeing the air pressure it expects across the combustion path. Navien names two owner checks: that the exhaust pipe is free of obstructions, and that the intake air filter is clean. Both are about the same thing — the unit's ability to move air through itself.
Does it matter which Navien you have?
NPE-2 and NPE-A / NPE-S all route code E110 the same way: a professional, at $0–$900. That makes it one of the Navien numbers you can act on before working out which unit you own.
What to check first, whatever your series
These checks are on the manufacturer's list for every Navien series that reports code E110, so they are safe to work through before you have identified your exact unit. They also cost nothing.
- Clean the intake air filter.
That is 1 of the 4 checks documented for code E110. The rest differ by generation, so if none of those explains it, go to your own series above.
Which Navien do you have?
On the 2 series that report code E110, the model number on the rating label starts NPE — match yours against the 13 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Navien NPE-2 User's Information Manual (p. 17), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Source: Navien NPE Operation Manual (NPE-A / NPE-S) (p. 16), read Aug 2026 — the manufacturer's own documentation for this Navien range.
Parts, guides and symptoms behind code E110
Code E110 on these 2 Navien series points at 1 guide, 2 parts and 3 symptoms, each named by the manufacturer's own procedure for this code.