Navien NCB300-28K Service Manual page 67

Testing method
Fault
Flame loss and noise
occurs after ignition
Flame loss and noise
occurs after ignition
Flame loss during Stage 2
Other faults
66 Troubleshooting
Possible causes
1. Check the gas supply pressure.
2. When static pressure is normal, the use of other gas appliances may cause
Low gas supply pressure Check the static pressure: Gas supply pressure in standby mode.
Check the dynamic pressure: Gas supply pressure at maximum combustion.
3. Check the gas pipe connections.
4. Check the gas meter rating.
Check the PCB DIP switch settings.
PCB DIP switch setting
error
Switch
1 & 2
Flame loss will occur if the gas orifices in the dual venturi are clogged.
Blockage in the gas
●
orifice plate.
PCB DIP switch setting
Check the PCB DIP switch settings.
errors * Check the correct resistance for flame detection AD.
PCB fault If the error conditions continue after checking these items, replace the PCB.
Testing method
NG: 17-25 mbar, LP: 25-35 mbar
●
LP pressure drop occurs frequently during winter.
●
the boiler's gas pressure to drop. Check the dynamic pressure.
If a CSST connector has been used, ensure that it has not been
●
overtightened. An overtight connection can deform the seal and
obstruct the flow of gas.
Function
Fuel selection
Remove the gas inlet pipe and check for debris inside the dual venturi.
Remove and clean the orifice plate if necessary.
1 2
O
N
Setting
LNG(G20) 1-OFF, 2-OFF
Not Used 1-OFF, 2-ON
LPG(G30) 1-ON, 2-OFF
LPG(G31) 1-ON, 2-ON