Green Flow Solution logo
Schedule Service

Product troubleshooting

Back to Navien NPF Series

Navien NPF Series troubleshooting and error codes

Use this table to identify what the visible code may mean and what information to share when scheduling service. Keep checks simple and visible; do not open electrical, refrigerant, gas, or sealed equipment compartments.

Schedule Service +1 (857) 767-6414

Error-code table

Search codes for NPF Series

Code Meaning System area Safe first step Action
E003 Ignition failure Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E004 False flame Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E012 Flame loss during operation Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E016 Heat exchanger overheat Equipment control Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E030 Abnormal exhaust temperature Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E031 Burner overheat Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E046 Heat exchanger overheating sensor issue Temperature / sensor Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E047 Exhaust thermostat issue Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E109 Abnormal inducer fan motor operation Airflow / fan Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E205 Heating supply temperature sensor Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E218 Heating return temperature sensor Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E238 Abnormal condensate or water-flow condition Water flow / hydronics Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E302 Low water level Water flow / hydronics Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E311 Abnormal water level Water flow / hydronics Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E351 Abnormal water fill Water flow / hydronics Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E360 Abnormal cover switch Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E515 Abnormal operation: PCB Controls / communication Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E517 Abnormal operation: DIP switch setting Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E593 Abnormal operation: front panel key Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E594 Abnormal operation: EEPROM Controls / communication Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E615 Abnormal operation: input and memory Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E740 Abnormal operation: outdoor temperature sensor Temperature / sensor Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E762 Improper vent pipe insertion Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E774 Manual reset limit Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E775 Auto reset limit Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E782 Abnormal operation: front/main panel communication Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E786 Improper front panel or panel connection Controls / communication Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E788 Abnormal gas type setting Combustion / venting Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E799 Abnormal appliance control operation Equipment control Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E805 Inverter or control protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E810 Inverter or compressor protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E811 Inverter or compressor protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E818 Voltage or inverter protection Refrigerant / inverter Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E822 Discharge or inverter protection Temperature / sensor Record the Navien code, avoid repeated reset attempts, and schedule GreenFlow service. View details
E860 Abnormal water or system control operation Water flow / hydronics Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details
E890 Abnormal circulator operation Water flow / hydronics Record the Navien code, check visible intake, exhaust, filter, thermostat, controller, and clearance conditions without opening panels, and schedule service if the condition remains. View details

Safety note

What is safe to check before service

These pages are meant to help document the issue, not replace diagnosis. GreenFlow should handle pressure-switch, electrical, refrigerant, lockout, recurring, and warranty-related conditions.

Safe visible checks

  • Thermostat display and settings
  • Filter condition and return-air path
  • Visible outdoor-unit obstruction
  • Photos of the code, unit, and nameplate

Stop and call

  • Repeated lockouts or recurring faults
  • Pressure-switch or sensor faults
  • Electrical odor, unusual noise, or ice buildup
  • Any sealed cabinet, refrigerant, gas, or warranty issue

Brands We Service

Popular cities

Service Areas

Our Happy Customers

Jack B.

Andrey always does a great job.

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...

Jahangir R.

They were very organized to communicate and be on time to come to look at my air condition to fix it.

Dev W.

I had a breakdown of my cooling system and Hanna at Green Flow responded to my request right away. They scheduled me same day. The team at Green Flow was easy to communicate with over phone and text. They kept me updated on delays on arrival of the...

View All