Navien E110 Error Code Explained: Causes, Troubleshooting, and Solutions
Learn what the E110 error means, its most common causes, how to fix airflow blockages, and ways to prevent the issue from returning.
ERROR CODES
6/16/20263 min read
Few things are more frustrating than stepping into the shower only to discover your Navien tankless water heater isn't producing hot water. If the display is showing Error Code E110, the unit is experiencing an air pressure or exhaust blockage problem.
In simple terms, the water heater cannot move combustion air properly through its intake and exhaust system. Since proper airflow is critical for safe operation, the unit automatically shuts down and displays the E110 error to prevent damage or unsafe conditions.
The good news is that many E110 issues can be resolved by identifying and removing airflow restrictions.
Why Does the E110 Error Occur?
A tankless water heater relies on a continuous flow of fresh air for combustion and a clear exhaust path to remove combustion gases. When either pathway becomes restricted, the pressure inside the system changes, causing the control board to trigger Error Code E110.
Think of it as the heater's way of saying:
"I can't breathe properly, so I'm shutting down until the problem is fixed."
Most Common Causes of Navien E110 Error
Blocked Air Intake Vent
The intake vent draws fresh air into the unit for combustion.
Common obstructions include:
Leaves
Dust accumulation
Spider webs
Bird nests
Plastic debris
Snow and ice during winter
Even a partial blockage can disrupt airflow enough to generate the error code.
Obstructed Exhaust Vent
The exhaust vent removes combustion gases from the system.
A blocked exhaust pipe can create excessive back pressure, preventing the unit from operating safely.
Potential causes include:
Debris buildup
Animal nests
Ice formation
Damaged vent pipes
Dirty Air Filter
Many Navien models include an air filter that protects internal components from dust and debris.
Over time, the filter can become clogged, restricting airflow and causing the E110 fault.
Faulty Air Pressure Sensor
The air pressure sensor monitors airflow within the combustion system.
If the sensor fails or provides inaccurate readings, the control board may incorrectly assume that an airflow problem exists.
Venting Installation Problems
Improper vent installation can also trigger E110.
Examples include:
Excessive vent length
Incorrect pipe sizing
Too many elbows in the vent system
Improper slope or termination
These issues reduce airflow efficiency and can create pressure imbalances.
Condensate Drain Blockage
Navien condensing water heaters produce condensate during operation.
If the condensate drain becomes clogged, moisture can accumulate and interfere with airflow within the combustion chamber.
How to Fix Navien Error Code E110
Start With a Simple Reset
Before performing any inspections:
Turn off the water heater.
Wait approximately five minutes.
Restore power.
Check whether the error returns.
Temporary sensor or communication issues may clear after a reset.
Inspect the Intake and Exhaust Vents
Examine all visible venting components.
Look for:
Dirt and debris
Animal nests
Ice buildup
Damaged vent sections
Blocked vent terminals
Remove any obstructions carefully and restart the unit.
Clean the Air Filter
A dirty air filter is one of the easiest problems to fix.
To clean the filter:
Turn off the unit.
Remove the filter according to the owner's manual.
Wash with clean water.
Allow it to dry completely.
Reinstall and restart the heater.
Regular filter maintenance helps prevent airflow-related shutdowns.
Check the Condensate Drain
Inspect the condensate line for:
Blockages
Kinks
Frozen sections
Standing water
Cleaning the drain can restore normal airflow and pressure conditions.
Inspect the Vent System
If the vents appear clear but the error persists, check for installation-related issues such as:
Sagging vent pipes
Loose connections
Excessive vent length
Improper vent termination
These problems often require professional correction.
Test the Air Pressure Sensor
If all airflow pathways are clear, the pressure sensor may be defective.
A technician can:
Verify sensor operation
Check electrical connections
Replace the sensor if necessary
Signs You Need Professional Service
While homeowners can often clear vent obstructions themselves, professional assistance is recommended if:
E110 returns repeatedly.
No visible blockage can be found.
Venting modifications are needed.
The pressure sensor is suspected to be faulty.
The unit frequently shuts down during operation.
Professional diagnosis can quickly identify less obvious airflow and combustion problems.
How to Prevent Error Code E110
The best way to avoid E110 is through routine maintenance.
Preventive Maintenance Checklist
✓ Inspect vent terminations every few months.
✓ Clean the air filter regularly.
✓ Flush the condensate drain annually.
✓ Remove debris around outdoor vent openings.
✓ Schedule annual maintenance inspections.
✓ Check for signs of vent damage after storms or severe weather.
Consistent maintenance helps ensure proper airflow and reliable performance throughout the year.
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