Navien NCB-180 Service Manual page 91

Check method
Fault Possible Causes
Flame loss and
Low gas supply
noise occurs after
ignition
PCB DIP switch
setting error
Flame loss and
noise occurs after
ignition
Offset pressure
adjustment error
88 NCB Service Manual
1. Check the gas supply pressure.
NG: 3.5" - 10.5" W.C, LP: 8" - 13.5" W.C

LP pressure drop occurs frequently in the winter.

2. While the static pressure is normal, the use of another gas appliance may cause a
possible drop in gas pressure to the unit. Therefore, it is required to check the
dynamic pressure.
Check the static pressure: Gas supply pressure during stand by.
Check the dynamic pressure: Gas supply pressure at (2nd stage MAX combustion setting:
DIP S/W 1-1 ON) MAX combustion
pressure
3. Check the gas pipe connector.
If a CSST connector has been used, check to ensure that it is not been

overtightened resulting in the seal obstructing gas flow.
4. Check the gas meter capacity (Example)
Gas meter

425 CFH (Gas Meter) ≥
195 CFH (Boiler)+ 58.8 CFH (Furnace)
CFH = 1,020 Btuh
Low fire (1-stage Min) offset adjustment error
Use the Front Panel to set the unit at "MIN.1" (refer to page 54).

Open the offset pressure port on the gas valve and connect a manometer.

Use the positive pressure side on a dual port manometer.
Adjust the offset pressure by turning the adjustment screw on the gas valve

with a 5/32" or 4mm Allen wrench, if the pressure value is out of range.
Check method
Boiler Furnace Domestic gas stove
+ 63.7 CFH (Domestic gas stove)
Check the PCB DIP switch settings.(Refer to page 21)
Version 1.0