Navien NFC-175, Service Manual

Page: 83 / 138

NFC Service Manual 83 Version 1.0
Fault Possible Causes Check method
Flame loss and noise
occurs after ignition
Digital pressure
manometer
Check the offset values for Min fire
Model Altitude Kit Part No. Gas
Type
Offset
NFC-175
NFC-200
0-5,399 ft NAC-N200
NG
-0.04 in
±0.01 in
5,400-
10,100 ft NAC-NCH200
0-10,100 ft NAC-LC200 LP
-0.02 in
±0.01 in
Offset value for low fire
Model Altitude Fuel
High fire Low fire
%CO
2
%CO
2
NFC-175
NFC-200
0-5,399 ft
NG 8.9 9.5
LP 10.2 10.8
5,400-10,100 ft
NG 8.5 9.5
LP 10.2 10.8
CO
2
value
Flame Rod
(Electrode)
Replace the electrode or clean the fire detecting electrode.
-
Cause: Due to the properties of the electrode, the oxide film is created due to
long-term exposure to the high temperature; therefore, errors may be caused
in detecting the fires.
-
Check-up: Use sandpaper to clean the fire detecting electrode covered with
oxide film or replace it.
Defected metal fiber
1. Check the presence of debris in the 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 during
2nd stage
Blockage in the gas
orifice plate.
Flame loss will occur if the gas orifices in the Dual Venturi are clogged.
●
Remove the gas inlet pipe and check for debris inside the Dual Venturi; remove
and clean the orifice plate if necessary.
Other trouble Defective PCB If the issue continues despite checking above items, replace the PCB.