Navien E110 Error Code: Exhaust Blockage and Venting Fault Explained

Quick Answer

Navien E110 is a venting fault. The sub-code tells you where: E110-01 means the outdoor vent termination cap is physically blocked by a bird nest, ice dam, or debris. E110-02 means the issue is inside, usually a kinked vent pipe, pipe that is too long, or a condensate drain that is backed up and pressurizing the flue. In winter, ice forming around the exhaust outlet from condensate drips is the single most common cause of E110 on Navien units. Clear the termination cap, check for ice, and reset the unit.

NavienWaterheaterSeverity: high82% DIY Success

Time to Fix

20–60 min

Difficulty

beginner

Parts Cost

$15 – $80

Tools Needed

Flashlight, Gloves and safety glasses

Wrong code?

Not seeing E110 on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

venting fault

Rinnai63

What Does the E110 Code Mean?

E110 means Navien's pressure switch detected an exhaust obstruction. The most common fix is removing ice, a bird nest, or debris from the outdoor vent cap. In winter, condensate freezing at the vent outlet is the leading culprit.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Bird nest or animal debris in vent termination cap40%

Ice dam forming around exhaust outlet in freezing temperatures24%

Kinked or crushed flexible vent pipe14%

Condensate drain line blocked, backing up into flue12%

Vent run exceeds maximum allowable length10%

Symptoms You May Notice

E110 or E110-01 / E110-02 on controller display
Unit attempts to fire then shuts down
Rumbling or restricted exhaust sound before lockout
Visible ice or blockage at outdoor vent cap in winter

Can you reset a Navien waterheater to clear the E110 code?

After clearing the vent blockage, press the Info button on the Navien controller 3 times to perform a soft reset. If the error persists, cut power at the breaker for 30 seconds and restore. Do not reset without first addressing the obstruction, as the code will immediately return.

Tools Required for Diagnosis

FlashlightGloves and safety glassesBucket and clean water (for condensate trap flush)Screwdriver (to access condensate trap)Heat gun or warm water (for ice removal only, never open flame)

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

Note the sub-code

Note the sub-code: E110-01 points to the outdoor vent termination; E110-02 points to an internal pressure fault. Go to the appropriate step based on the sub-code.

Go to the outdoor vent termination cap

Trace the vent pipe from the unit to the termination cap

For E110-02

After clearing any obstruction or fault

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name	OEM Number	Estimated Price
Vent Termination Cap (2-inch, PVC)BH-2T (various, check vent brand) · $15–$40	BH-2T (various, check vent brand)	$15 – $40
Condensate Trap Kit30010723A · $20–$35	30010723A	$20 – $35
Air Pressure Switch30010617A · $45–$80	30010617A	$45 – $80

Verify part fitment for your Navien model

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs

Labor Approach

Our Verdict

REPAIR

Estimated Cost: $48 (Parts) vs $1100 (New Machine)

Frequently Asked Questions

Why does my Navien show E110 only in winter?

Navien condensing water heaters produce liquid condensate as a byproduct of the high-efficiency combustion process. In freezing temperatures, this condensate can drip from the exhaust outlet and accumulate as ice around the vent termination cap, eventually blocking the opening enough to trigger E110. Adding a freeze-resistant vent termination cap or sloping the vent pipe properly to drain condensate back toward the unit's trap can prevent this.

What is the difference between E110-01 and E110-02?

E110-01 means the pressure switch detected a restriction on the exhaust side at or near the termination, usually a physical blockage. E110-02 indicates the pressure differential inside the unit is out of range without a clear external obstruction, pointing to a kinked vent pipe, a pipe run that is too long, or an internal issue with the condensate trap or air pressure switch itself.

Can I use a heat gun to melt ice at the vent termination?

A heat gun on low setting can melt ice at the PVC termination cap, but keep it moving and do not concentrate heat on one spot. Never use an open flame. Warm water poured over the cap is safer and equally effective. After clearing the ice, consider insulating the exposed vent pipe in the wall or eave cavity to reduce condensate freezing.

How often should I inspect the Navien vent termination?

Once per year at minimum, ideally before winter. In areas with active bird populations, check in early spring and again in late summer. If you have had one E110 event from a bird nest or ice, inspect every season since the same conditions will recur.

My vent termination is clear but E110 keeps coming back. What now?

If the cap is clear and the pipe has no kinks, the next suspects are total vent length exceeding Navien's maximum for your pipe diameter, too many elbows in the run, or a faulty air pressure switch inside the unit. Check your installation manual for maximum equivalent feet. For a 2-inch PVC run, Navien's max is typically 60 equivalent feet. If you are within spec, the pressure switch may need replacement.

Related Navien Waterheater Error Codes

Code: HUBNavien Tankless Water Heater Error Codes: Complete NPE and NCB Series Guide Code: E773Navien E773 Error Code: Exhaust Overheat Thermal Limit Code: RESETHow to Reset a Navien Tankless Water Heater and Clear Error Codes

Same Fix on Other Brands

Rinnai waterheater63: Rinnai Code 63: Combustion Fan Error

Models Known to Experience E110 Errors

This repair applies to most Navien waterheaters with this error code. Common model numbers include:

NPE-240A, NPE-180A, NPE-210A, NCB-240E, NPN-199A

Last verified for technical accuracy on March 14, 2026