- Boilers
- Tankless gas water heater
E110
Navien E110 on a tankless water heater: abnormal air pressure
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
The heater detected abnormal air pressure in its air or exhaust path. Navien's actions are to make sure the exhaust pipe is free of obstructions and to clean the intake air filter. Check the terminal from outside and call a technician.
Safety first
Stop and check this first
- If you smell gas: do not try to light any appliance, do not touch any electrical switch and do not use any phone in the building. Call your gas supplier from a neighbor's phone and follow its instructions; if you cannot reach it, call the fire department.
- Do not remove the front cover to look inside: Navien warns that operating the heater with the front cover open can cause fire or carbon monoxide poisoning, and that the cover may only come off with the power disconnected.
Safe checks you can perform
- Exhaust and intake terminals outside
- One reset with the Back button
- Possible freezing
- Intake air filter cleaning
Leave these tasks to a qualified professional
- Do not attempt this professional task: Clean the intake air filter
- Do not attempt this professional task: Inspect exhaust and intake piping
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Clean the intake air filter
What they doThe technician cleans the filter behind the front cover with power disconnected.
They must show youthe filter before cleaning.
In writingdate of cleaning.
Inspect exhaust and intake piping
What they doThe professional checks terminals and piping for obstruction, accumulation of exhaust and clearances against the installation manual.
They must show youphotos of what was found.
In writingwhat was corrected.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Exhaust and intake terminals outside
- Who:
- you.
- How:
- from the ground or a window, look at the terminals without touching them. Navien says not to place anything in or around the vent terminals that could obstruct air flow.
- Result that matters:
- whether something blocks them.
- If something at ground level is placed near the terminal:
- move it away and reset once.
- If the terminal itself is blocked or out of reach:
- turn the heater off and call a technician.
- Evidence to keep:
- photo of the terminals.
Do not climb to a roof terminal or disconnect vent pipes.
Evidence: Navien NPE-A2 and NPE-S2 installation and operation manual
One reset with the Back button
- Who:
- you.
- How:
- press the Back button on the front panel. Navien's manual says resetting may solve the problem when an error appears.
- Result that matters:
- whether E110 comes back.
- If the heater runs normally:
- note the date; if E110 returns later, mention that it was reset before.
- If E110 returns:
- do not keep resetting; Navien says to contact an authorized technician, a licensed professional or its technical support.
- Evidence to keep:
- photo of the code before and after the reset.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
Possible freezing
- Who:
- you.
- How:
- consider whether there was freezing weather. Navien links E110 and E003 to frozen units.
- Result that matters:
- whether freezing is plausible.
- If it is:
- turn the heater off with the Power button, close the gas valve, open the hot water faucet closest to the heater and call a technician.
- If not:
- filter or vent branch is more likely.
- Evidence to keep:
- date and temperature.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual · Navien preventing a frozen tankless water heater
Intake air filter cleaning
- Who:
- the installer or a technician.
- How:
- with the heater off and power disconnected, removes the front cover and cleans the intake air filter, as Navien's manual describes.
- Result that matters:
- whether E110 clears.
- If it clears:
- record the date; Navien recommends cleaning every 3 to 4 months.
- If it does not:
- the vent system must be inspected.
- Evidence to keep:
- photo of the filter.
This requires removing the front cover of a gas appliance. We recommend leaving it to a technician.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual · Navien NPE-A2 and NPE-S2 installation and operation manual
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Boilers
- Brand
- Navien
- Product type
- Tankless gas water heater
Known code variants
- 110
- Baxi 110
- Baxi E 110
- calentador Navien E110
- Error 110 Baxi
- Error Code 110
- Navien 110
- Navien E110
- Navien E110 air pressure
- Navien E110 presión de aire
- Navien error E110
- Platinum Compact 110
What it means
Navien defines E110 as abnormal air pressure. Its owner actions are ensuring the exhaust pipe is free of obstructions and cleaning the intake air filter; the manual adds that a clogged filter stops the heater with this code. Navien also lists E110 among codes a frozen unit can store. The filter sits behind the front cover, so we recommend a technician cleans it. The code does not identify a failed part.
Warnings and stop conditions
- Criticalsource verified
If you smell gas: do not try to light any appliance, do not touch any electrical switch and do not use any phone in the building. Call your gas supplier from a neighbor's phone and follow its instructions; if you cannot reach it, call the fire department.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
- Highsource verified
Do not remove the front cover to look inside: Navien warns that operating the heater with the front cover open can cause fire or carbon monoxide poisoning, and that the cover may only come off with the power disconnected.
Evidence: Navien NPE-A2 and NPE-S2 installation and operation manual
Symptoms and causes
Probable causes · in order
- Obstructed exhaust or intake terminalPossible
Navien's first action. Snow, ice, nests or objects near the terminal fit this branch.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual · Navien NPE-A2 and NPE-S2 installation and operation manual
- Clogged intake air filterPossible
Navien says a filter clogged by dust or lint stops the heater with E110.
Evidence: Navien NPE-A2 and NPE-S2 user's information manual
- Unit frozenPossible
Navien links air intake blockage (E110) to freezing. Fits after a hard frost.
Evidence: Navien preventing a frozen tankless water heater
Virtual technician
Does E110 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Navien NPE-A2 and NPE-S2 user's information manual
Navien · 2020 · manual
- 2
Navien NPE-A2 and NPE-S2 installation and operation manual
Navien · 2026 · manual
- 3
Navien preventing a frozen tankless water heater
Navien · 2024 · official_doc
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