Navien E110 Error Code: Abnormal air pressure
Updated October 2026 · Sourced from Navien documentation
The unit sees abnormal air pressure. The manual says to make sure the exhaust pipe is free of obstructions and to clean the intake air filter. A clogged filter stops the unit and shows this code.
Is it safe to keep running? Check the steps below first. If the code returns, call a licensed technician to inspect the vent system and fan.
E110 at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| E110 Error code shown on the front panel display | Abnormal air pressure | NPE-180A2, NPE-210A2, NPE-240A2, NPE-180S2, NPE-210S2, NPE-240S2 condensing tankless water heaters |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Look at the outside exhaust and intake terminals for blockage such as leaves, snow or nests. Do not climb or open vent pipes.
- Clean the air intake filter (manual section 4.5). The manual advises cleaning it every 3 to 4 months.
🛑 Stop and call a licensed pro if
- If the code returns, call a licensed technician to inspect the vent system and fan.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Codes for flame failure, overheating, venting or the control board that return after one reset.
- Water leaking from the heater, the relief valve discharging, or scorching around the burner area.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any Navien code
- Write down the exact code shown on the controller or the number of status light flashes.
- Turn the water heater power off and back on (or press the reset button the manual describes) once. If the code comes back, stop resetting.
- Make sure the gas supply valve to the heater is open and other gas appliances in the home are working.
- Make sure the cold water supply valve is fully open and hot water taps are not partly closed.
- Look at the outside vent terminal for snow, ice, leaves or anything blocking it (look only).
Source: Navien NPE Condensing Water Heaters User's Information Manual (NPE-2, rev 201202), 5.2 Understanding Error Codes, p.17. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
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