Understanding Error Codes - Navien NFC-250/200H User's Information Manual

5.2 Understanding Error Codes

When an error code appears on the front panel, refer to the following chart for a definition and possible remedy
for the situation.
Error Code Reason
E001 Heatexchanger over temperature
E003 Ignition failure
E004 False flame detection
E012 Flame loss
E016 Overheating of heat exchanger
E030 Abnormal exhaust temperature
E031 Overheating of burner
E046 Abnormal operation: heat exchanger overheating sensor
E047 Abnormal operation: exhaust thermostat
E060 Abnormal operation: dual venturi
E109 Abnormal operation: fan motor
E110 Abnormal air pressure
E205 Abnormal operation: heating supply thermistor
E218 Abnormal operation: heating return thermistor
E278 Abnormal operation: system supply thermistor
E279 Abnormal operation: system return thermistor
E351 Abnormal Auto feeder valve (make-up water)
E352 High water pressure
E353 Abnormal operation: water pressure sensor
E407 Hot water outlet: thermistor open or short circuit
E421 Cold water inlet: thermistor open or short circuit
E434 Abnormal operation: water adjustment valve
E439 Abnormal operation: flow sensor
E441 Hot water outlet 2: thermistor open or short circuit
E445 Abnormal operation: Bypass mixing valve
E515 Abnormal operation: PCB component
E517 Abnormal operation: Dip switch setting
E594 Abnormal operation: EEPROM
24 Troubleshooting
Self-diagnostic/Action
Manual RESET
Auto RESET
Manual RESET
Manual RESET
Auto RESET
Manual RESET
Manual RESET
Manual RESET
Alarm
Manual RESET
Auto RESET
Manual RESET
Auto RESET
Alarm
Manual RESET
Manual RESET
Auto RESET
Auto RESET
Alarm
Alarm
Manual RESET
Auto RESET
Auto RESET
Auto RESET
Auto RESET
Alarm
Alarm
Auto RESET
Alarm
Manual RESET
Alarm
Manual RESET
Alarm