Navien E110 Error Code — What It Means
E110 is an abnormal air pressure or airflow fault on Navien tankless water heaters. The unit is not proving the expected combustion air and exhaust pressure condition, so it locks out to protect safe operation. In practical terms, the heater is not getting or moving air the way its pressure-sensing logic expects, and it stops heating until the problem is corrected.
Common Causes
- Blocked outdoor vent or intake termination Snow, ice, leaves, dirt, bird nesting, or other debris obstructing the exterior intake or exhaust pipe is the most common field cause.
- Dirty internal air intake filter The air filter behind the front cover becomes clogged with dust and lint over time, restricting airflow and triggering the pressure fault.
- Restricted condensate trap or drain line Sediment buildup, sludge, or standing water in the condensate trap or drain path affects pressure behavior and can cause recurring E110 faults.
- Venting installation problems Improper vent termination, blocked flue, or pressure imbalance from installation errors prevents correct airflow and pressure readings.
- Air pressure sensing or control component fault If the mechanical airflow path is clear, internal air pressure sensing or control components may have failed and require professional diagnosis.
Step-by-Step Fix
- Power down the unit completely and wait for it to cool before opening any panels or performing work.
- Inspect the exterior vent and intake terminations for snow, ice, leaves, bird nests, or other debris and clear any obstruction you find.
- Remove and clean the internal air filter by opening the front cover, washing the filter with water, drying it completely, and reinstalling it.
- Check the condensate trap and drain line for sludge, scale, or standing water and clean or flush the trap and drain path as needed.
- Restore power and reset the heater to see if it runs normally after clearing the airflow path.
- Monitor for repeated faults and if E110 returns immediately, check for venting design issues or call a professional for internal air pressure system diagnosis.
- Document the outdoor temperature and conditions when the fault occurs, as ice and snow are common seasonal triggers that may require vent relocation or shielding.
Parts Often Needed
| Part | Notes |
|---|---|
| Navien air intake filter | Amazon | Internal foam or mesh filter behind the front cover, wash and dry or replace if torn or heavily fouled. |
| Condensate trap and drain kit | Amazon | Replace if cracked, fouled beyond cleaning, or if sediment buildup is chronic. |
| Vent termination cap or shield | Amazon | Consider an upgraded or shielded termination if snow and ice blockage is a recurring problem in your climate. |
When to Call a Pro
Call a professional if the E110 code returns immediately after you have cleared all visible obstructions, cleaned the air filter, and flushed the condensate system. Persistent faults point to venting installation errors, air pressure sensor failures, or internal control component problems that require diagnostic equipment and access to manufacturer service data. A licensed technician can verify proper vent sizing and termination, test air pressure sensing circuits, and replace internal components safely.