Green Flow Solution logo
Schedule Service

Troubleshooting code

Back to all NFC-H Series error codes

Navien NFC-H Series E407 troubleshooting

Domestic hot water outlet thermistor open or short. Use this page to document the issue and prepare for service. GreenFlow should handle diagnosis for electrical, refrigerant, lockout, or recurring conditions.

Schedule Service +1 (857) 767-6414

What the code means

E407: Domestic hot water outlet thermistor open or short

The Navien manual for this product family lists E407 as: Domestic hot water outlet thermistor open or short.

System area
Temperature / sensor
Service level
Service recommended

Safe checks before calling

  • Record the exact Navien code, whether the unit is locked out, and when the code appeared.
  • Confirm thermostat, controller, or front-panel status without changing service settings.
  • Check only visible intake, exhaust, filter, clearance, condensate, and water-supply conditions that can be inspected without opening panels.
  • Take photos of the code, equipment nameplate, venting, surrounding equipment area, thermostat or controller, and any visible leak, ice, or obstruction.

When to stop and call GreenFlow

Call GreenFlow if the code repeats, the unit is locked out, hot water, heating, or cooling is not restored, or the concern involves gas, flame, combustion, venting, electrical components, refrigerant, pressure, water leaks, PCB/control boards, sensors, pumps, or warranty coverage.

Share the visible code, model and serial number if available, photos, current symptoms, and whether the issue affects heating, cooling, or both.

E407 questions

What does E407 mean on a Navien NFC-H Series?

The Navien manual for this product family lists E407 as: Domestic hot water outlet thermistor open or short.

What should I safely check before scheduling service?

Record the displayed code, confirm thermostat or controller status, check only visible intake, exhaust, filter, clearance, and water-supply conditions, and take photos of the code and nameplate. Do not open gas, electrical, refrigerant, combustion, or internal equipment panels.

When should GreenFlow handle this code?

Call GreenFlow if the code repeats, the unit is locked out, hot water, heating, or cooling is not restored, or the concern involves gas, flame, combustion, venting, electrical components, refrigerant, pressure, water leaks, PCB/control boards, sensors, pumps, or warranty coverage.

Brands We Service

Popular cities

Service Areas

Our Happy Customers

Neal V.

In an industry that often fraught with contractors taking advantage of homeowners, Andrey was honest with his assessment and willing to install a product acquired elsewhere (most want that margin themselves), patiently answered my questions (I’m an engineer so like to understand what’s happening), and proactively offered practical...

Michele Z.

Andrey was professional, prompt, smart, thorough and exceedingly pleasant. We are likely switching our current HVAC company to Green Flow.

Randy J.

Thanks to Andrey for an amazingly quick response to my request for a service call. He diagnosed and fixed my issue within 24 hours of my asking for help. Excellent service. Thanks.

Michael C.

always available, easy to get a hold of, as a property manager I get lots no heat emergency, usually get to it same day or next day

View All