DIY Error Codes

Navien NPE-2 tankless water heater Error E110

Air flow through the heater is abnormal. Navien says check the exhaust for obstructions and clean the air intake filter.

Navien's listed fixes: make sure the exhaust pipe is free of obstructions and clean the air intake filter.

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Full answer & models

Navien E110 on the NPE-2 means: abnormal air pressure. Navien's listed fixes: make sure the exhaust pipe is free of obstructions and clean the air intake filter.

Applies to: NPE-180A2NPE-210A2NPE-240A2NPE-180S2NPE-210S2NPE-240S2
Also searched as: Navien error E110, Navien E110, Navien error code 110, Navien 110 code

Gas appliance. Power off and let it cool before any maintenance.
Why
If you smell gas: do not try to light any appliance, do not touch any electrical switch, and do not use any phone in your building. Leave and call your gas supplier from a neighbor's phone; if you cannot reach them, call the fire department. Navien: turn the water heater off and disconnect the power supply before maintenance. It can stay hot for several minutes after it is turned off; wait until it cools to avoid burns. Water at or above 125 °F (52 °C) can cause instant scalding, severe burns, or death.

What E110 means

Air flow through the heater is abnormal. Navien says check the exhaust for obstructions and clean the air intake filter.

More detail
Navien's error-code chart (section 5.2) lists E110 as "abnormal air pressure". Navien's maintenance section adds that if the air intake filter becomes clogged by dust or lint, the heater will stop and display Error Code 110. If the listed remedies do not resolve the problem, Navien says to contact Technical Support.

5-minute checks

Fix it step by step

Step 1 of 3

  1. Check the exhaust for obstructions

    • 5 min
    • None
    • DIY

    Look at the outdoor termination only. Do not disconnect vent pipe.

    More detail

    Check the exhaust for obstructions.

    Navien chart, E110: ensure that the exhaust pipe is free of obstructions.

    Did the code clear?

  2. Clean the air intake filter

    • 20 min
    • Screwdriver, Toothbrush
    • DIY

    Safety: Gas appliance. Power off and let it cool before any maintenance.

    Power off, unplug, remove the front cover, take out the filter (top left), wash and dry it.

    More detail

    Clean the air intake filter.

    Navien section 4.5: press Power to turn the heater off, disconnect the power supply, remove the front cover, remove the screw holding the air intake filter (top left), pull it out, separate it from the plastic assembly, clean it with a toothbrush and clean running water, let it dry completely, then reassemble, replace the cover, reconnect power and turn it on. Navien recommends cleaning this filter every 3-4 months.

    Did the code clear?

  3. Call a licensed pro

    • Decision
    • None
    • Pro decision

    Stop here and book a qualified technician.

    More detail

    Call a licensed pro.

    If E110 returns with a clear vent and clean filter, have a licensed technician inspect the venting.

    Still showing E110?Need a pro → call a pro

Code cleared. Nice work.

Watch the display for a day to make sure it stays clear.

Back to top

Fixed after any step? Watch the display for a day to make sure it stays clear. Still E110 after step 3? call a pro.

Call a pro if…

  • The vent pipe looks damaged, disconnected or blocked inside.
  • E110 returns after the filter is cleaned.

FAQ

What does Navien E110 mean?

Abnormal air pressure, per the NPE-2 chart.

Why does a dirty filter cause E110?

Navien's manual says a clogged air intake filter will stop the heater and show error code 110.

Source: Navien NPE-2 User's Information Manual (NPE-A2/NPE-S2), Section 5.2 Understanding Error Codes, Sections 4.2-4.5 Maintenance. Written by the DIY Error Codes team. Updated 2026-10-16. DIY Error Codes is independent and not affiliated with or endorsed by Navien.