Navien NCB500-2S/37K Service Manual page 60

Error Code Sub Code
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 Diagnosis/Actions
Troubleshooting 59