Navien NCB-180, Service Manual

Page: 92 / 149

Fault Possible Causes Check method
Flame loss and
noise occurs after
ignition
Flame loss during
2nd stage
Blockage in the
gas orifice plate.
Flame loss will occur if the gas orifices are clogged.

Remove the gas inlet pipe and check for debris; remove and clean the orifice
plate if necessary.
Other trouble
PCB DIP switch
setting error
Check the PCB DIP switch settings.(Refer to page 19)
Defective PCB
If the issue continues despite checking above items, replace the PCB.
* Check the flame detection AD
value for proper resistance.
(refer to page 42~43)
Check the offset values for low fire
Offset value for low fire
Model Gas Type Offset
NCB-180
NG -0.04"±0.01"
LP -0.03"±0.01"
NCB-210
NG -0.04"±0.01"
LP -0.02"±0.01"
NCB-240
NG -0.04"±0.01"
LP -0.02"±0.01"
Digital pressure
manometer