E279 🟡 Repair Required
Navien Error Code E279: Mixing Valve Open Failure
⚠️ Your Navien boiler has detected a failure in the mixing valve, which could lead to system damage if not addressed.
How to Fix Navien Code E279
- Step 1: Check if your boiler is receiving power. If not, reset the power by turning off the breaker for a few minutes and then turning it back on.
- Step 2: Inspect the mixing valve for any visible damage or leaks. If you find any, do not attempt to fix it yourself and call a professional immediately.
- Step 3: If the problem persists, call a licensed HVAC technician to diagnose and repair the issue.
What Does Navien Error Code E279 Mean?
The E279 error on your Navien boiler indicates a problem with the mixing valve's open circuit. The mixing valve is responsible for blending the hot water from the boiler with the cold water coming into your home. If it's not opening correctly, your boiler can't provide hot water, and you might notice a lack of hot water or reduced water temperature. This issue is typically caused by a faulty valve or a problem with the wiring or control board connected to it.
Common Causes of Navien Code E279
- Faulty mixing valve
- Wiring issue between the mixing valve and control board
- Problem with the control board itself
Applicable Navien Models
Source Documentation
This error code is documented in 5 official Navien technical manuals.
NFB-H Installation & Operation ManualPage 116
ReasonExt. Return Sensor Not Detected
ActionCheck sensor connections.
Navien NCB-H Installation & Operation ManualPage 129
ReasonExt. Return Sensor Not Detected
ActionContact technical support at 1-800-519-8794.
Navien NFB-H Installation & Operation ManualPage 116
ReasonExt. Return Sensor Not Detected
ActionCheck sensor connections.
Navien NFC-H Installation & Operation ManualPage 127
ReasonAbnormal operation: system return thermistor
ActionAlarm
Navien NHB-H Installation & Operation ManualPage 119
ReasonExt. Return Sensor Not Detected
ActionCheck sensor connections.
Need a Pro to Fix Navien Code E279?
A licensed HVAC technician can diagnose and fix this issue quickly.
Find a Licensed Tech Near You →Replacement Parts for Navien Tankless Water Heater Code E279
Mixing Valve OEM: 3201100010
Control Board OEM: 3201200010