Navien NHB-055 Service Manual page 95

Fault
Flame loss during
2nd stage
Other trouble
Version 1.0
Possible Causes
[Location of assembly screw and ground bolt in heat exchanger]
1. Check the presence of debris in the metal fiber.
Defected metal fiber
2. Check the sagging of the metal fiber and then the gaps with the electrode.
[Gap between the electrode and metal fiber: 12mm]
Flame loss will occur if the gas orifices in the Dual Venturi are clogged.
Blockage in the gas
Remove the gas inlet pipe and check for debris inside the Dual Venturi; remove
●
orifice plate.
and clean the orifice plate if necessary.
Defective PCB If the issue continues despite checking above items, replace the PCB.
Check method
NHB Service Manual 95