Navien Tankless Water Heater Error Code E110: Meaning & How to Fix It

By the ErrorCodePro Editorial Team · Last reviewed October 20, 2026

Navien tankless water heater error code E110 means: Abnormal air pressure in the combustion air system. [1] Keep using it? No hot water until it's resolved. Don't keep resetting it.. Start with the owner checks below, beginning with: check the vent terminals.

Smell gas? Leave the building now. Do not touch light switches, phones or appliances inside. Call your gas utility or 911 from outside. CO alarm sounding or headache, dizziness or nausea? Get everyone outside and call 911. Gas valves, burners, venting and wiring are for a licensed technician only. See our safety policy.

Quick facts

Code	E110
Also shown as	None listed by the manufacturer
Brand / appliance	Navien tankless water heater (npe-2 condensing tankless water heaters)
System	Venting / airflow
Official meaning	Abnormal air pressure in the combustion air system. [1]
Keep using it?	No hot water until it's resolved. Don't keep resetting it.
DIY-safe?	Owner checks only (listed below)
Support	Navien Technical Support, 1-800-519-8794

On this page: Meaning · Steps · Parts · When to call a technician · Related codes · FAQ

What error code E110 means on a Navien tankless water heater

Abnormal air pressure in the combustion air system. [1]

This is a venting / airflow code. Codes and wording can vary by model, so check your owner's manual for your model number.

How to fix Navien tankless water heater error code E110 (safe owner checks)

Owner checks only: on heating, cooling and water-heating equipment, limit yourself to reading the code and checking the thermostat, breaker and service switch, air filter, condensate drain, that the gas supply valve is open (no disassembly) and that vent terminals are clear of snow or debris. Reset power only if your manual allows it.

Safety first: disconnect power before you remove any panel or reach into the sump or drum. Do not touch wiring, the control board or the motor. If you see water near electrical parts, stop and call a technician. These steps are based on Navien's published guidance [1], rewritten for clarity.

Check the vent terminals. Outside, make sure the intake and exhaust terminals are free of snow, ice, leaves, nests or other obstructions. Don't disconnect any vent pipe.
Clean the intake air filter. Clean the intake air filter (see the manual).

Parts that may be involved

Exact parts depend on your model number. This page lists part types only, never part numbers.

No specific part is implied by the manufacturer's guidance for this code.

When to call a technician

Venting problems are a carbon monoxide risk: technician
Gas pressure, gas valve, igniter, flame rod, venting or combustion problems: licensed plumber or gas technician
Gas valves, burners, igniters, flame sensors, venting/flue or CO concerns: licensed HVAC technician or plumber
Refrigerant work: EPA 608-certified technician only
Smell of gas: leave and call the gas utility or 911
Anything involving wiring, the control board, the motor or the water valve electrics
The appliance is under warranty: contact Navien Technical Support, 1-800-519-8794 first

Frequently asked questions

What does error code E110 mean on a Navien tankless water heater?

Navien lists E110 as follows: Abnormal air pressure in the combustion air system.

Is it safe to keep using the tankless water heater with E110?

No hot water until it's resolved. Don't keep resetting it..

Can I fix Navien tankless water heater error E110 myself?

Only with the owner checks on this page, starting with: check the vent terminals. If it persists, call a technician or Navien Technical Support, 1-800-519-8794.

Sources

https://www.navieninc.com/downloads/npe-2-user-s-information-manual-en/download (official)

Last reviewed: October 20, 2026. ErrorCodePro is not affiliated with Navien.