Navien NCB300-28K Service Manual page 56

Error Code Sub Code
Heating supply thermistor open
1
error
E205
Heating supply thermistor short
2
error
E302 0 Low water pressure
Hot water outlet thermistor open
1
error
E407
Hot water outlet thermistor short
2
error
Abnormal operation: Relay
E515
feedback (PCB)
Abnormal operation: DIP switch
E517 0
setting (PCB)
Abnormal operation: EEPROM
E594 0
(PCB)
Abnormal operation: Input and
E615
memory (MCU)
Abnormal operation: Outdoor
E740 1
temperature sensor
Abnormal operation: Main panel
E782 0
communication
Abnormal operation: OpenTherm
E783 0
remote control
E787 1 Abnormal operation: Reset device
Abnormal operation: Gas type
E788 0
settings
If the actions contained in the table above do not resolve the boiler fault, contact the Navien technical support team on 1-800-519-8794.
To assist with fault resolution, error codes are displayed on the front panel and saved on a PCB board in the boiler providing a record of
the faults and failures that occur.
IMPORTANT
To reset the boiler, either press [Reset] on the front panel or turn off the boiler's power supply and then turn it on again.
Function
1. Check the thermistor.
2. Check pump wiring connections.
1. Check filling loop and pressurise system to 1.0 - 1.3 bar.
2. Check the incoming water pressure and activity at the PRV.
1. Check the thermistor.
2. Replace the thermistor.
Check the dip switches on the front panel and the PCB.
Check the PCB.
1. Ensure that outdoor reset curve is correctly configured.
2. Check the outdoor temperature sensor's wiring connections.
Check the PCB.
Diagnosis/Actions
Troubleshooting 55