Navien E027 Error Code — What It Means
The E027 code on a Navien tankless water heater indicates an abnormal air pressure sensor condition. The control board is receiving a signal from the air/pressure sensing circuit that does not match expected operating conditions. This sensor verifies combustion air supply and proper venting during operation.
In practical terms, the heater has detected a problem with airflow or the sensor itself. The fault prevents safe combustion, so the unit will lock out until the condition is cleared. Always verify the exact code behavior in your specific model’s manual, as Navien notes that code meanings can vary across product lines.
Common Causes
- Blocked or restricted venting Exhaust or intake vent pipes obstructed by debris, nests, ice, or improper termination are the most commonly cited field cause.
- Dirty or clogged air filter Combustion air filter loaded with dust restricts airflow and triggers an abnormal pressure reading.
- Faulty air pressure sensor The sensor itself may be out of spec, intermittent, or failed when venting and filter checks pass.
- Combustion path restriction Internal airflow blockage or maintenance-related issues can prevent normal air movement through the heater.
Step-by-Step Fix
- Verify your model and code behavior by checking the service manual for your specific Navien unit, as code definitions can vary.
- Inspect intake and exhaust venting for blockage, disconnection, crushing, or improper outdoor termination that restricts airflow.
- Remove and inspect the air filter at the combustion-air inlet, then clean or replace it if loaded with dust or debris.
- Clear any obstruction in the vent or combustion-air path and confirm the heater can draw and exhaust air normally.
- Test the air pressure sensor circuit and its wiring connectors for intermittent contact, corrosion, or out-of-spec readings if the fault persists after airflow corrections.
- Replace the air pressure sensor if testing shows abnormal or erratic signals and all vent and filter checks are normal.
- Run the heater through a full heating cycle and confirm the E027 code clears and the unit operates normally.
Parts Often Needed
| Part | Notes |
|---|---|
| Air pressure sensor | Amazon | Order by your exact Navien model number when venting and filter checks pass but code remains. |
| Air filter | Amazon | Many models use a cleanable filter, but replace if damaged or non-serviceable. |
When to Call a Pro
Call a licensed technician if you have cleared the venting and cleaned the air filter but the E027 code returns. Testing the air pressure sensor circuit requires a multimeter and familiarity with Navien control boards. Combustion appliances involve gas, high voltage, and carbon-monoxide risk, so any work beyond basic filter and vent inspection should be handled by qualified service personnel. If your unit is under warranty, contact Navien or an authorized service center before replacing parts.