Navien NCB-180 Service Manual page 88

Failure
Cause
mode
Flame sensing error
Repeated
ignition-out
Flame loss
Check if there are any
and noise
blockages in the gas
occurs at
orifice plate.
ignition
Improper air
intake air Rainwater intrusion
supply
Screw loosening
Other
trouble
Defective PCB
1. Check the location of the flame, if there is any deformation or foreign substance,
repair or replace the part.
2. Check the flame rod wire for proper connection and/or damage.
3. Check the grounding to the boiler case to verify proper grounding at the outlet.
If the ground wire is improperly connected or not making a good connection,

remove and reattach the ground wire ensuring good contact with the case.
Or use a multi-meter to measure the flame sensing current (normally 3~4 µA).

Measuring flame current
Ignition failure will occur if the gas orifices are clogged.
Remove the gas inlet pipe and check the orifice plate.

Check if rainwater has collected inside the unit from an improperly installed air intake
pipe.
Tighten the ground connection screws on heat exchanger.
If the issue continues despite checking above items, replace the PCB.
Check method
Grounding wire position