Navien E205: H/E Outlet Sensor Error
Hot water temperature has been drifting — a little too hot, a little too cold, inconsistent from one draw to the next — and now E205 sits on the display. This code doesn't mean the unit lost heat entirely; it means one of the sensors it relies on to control temperature stopped reporting a believable number.
Applies to: Navien NPE, NCB, and NHB tankless and combi/condensing water heaters
What it means
H/E Outlet Error — the heat exchanger outlet (supply) temperature sensor is open or shorted. The outlet sensor is one of the readings the control board leans on to decide how hard to fire the burner, so a bad reading here can show up as inconsistent output for a while before it ever throws this code.
Most common causes
- Failed thermistor
- Damaged sensor wiring or connector
What you can safely check yourself
- No safe homeowner repair — this is a sensor replacement job
When to call a professional
This code appears — a technician needs to test and likely replace the thermistor.
Gas supply lines, gas control valves, and venting should only be worked on by a licensed plumber or HVAC technician. Mains/line-voltage electrical work should be done with the breaker off and, beyond a simple reset, by a qualified electrician or plumber.
What the fix costs
Sensor replacements like this one tend to sit toward the lower end of water heater repair costs — often $75–$250 for a straightforward thermistor swap once it's diagnosed (HomeGuide, Angi) — though a full diagnostic visit that includes locating and testing the sensor can run up to the more typical $150–$600 range depending on the technician's rates and how accessible the sensor is.
Related codes
- Navien E016 — Heat Exchanger Overheating
- Navien E515 — PCB Error
- Water not hot enough or runs lukewarm
All Navien codes
Every Navien water heater fault code — the full list on one page.
Sources
- Navien NPE/NCB/NHB owner's manual and error code troubleshooting guide (manufacturer documentation)