Navien NCB-180, Service Manual

Page: 88 / 149

Failure
mode
Cause Check method
Repeated
ignition-out
Flame sensing error
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 Grounding wire position
Flame loss
and noise
occurs at
ignition
Check if there are any
blockages in the gas
orifice plate.
Ignition failure will occur if the gas orifices are clogged.

Remove the gas inlet pipe and check the orifice plate.
Improper air
intake air
supply
Rainwater intrusion
Check if rainwater has collected inside the unit from an improperly installed air intake
pipe.
Other
trouble
Screw loosening
Tighten the ground connection screws on heat exchanger.
Defective PCB
If the issue continues despite checking above items, replace the PCB.