Navien NCB-180 Service Manual page 30

7. Remove the PCB assembly.
Figure 3. Access to Gas Orifice in Fan Assembly
8. With the internal components exposed, locate the gas inlet
pipe and the gas valve in the middle of the unit, as shown
below
Gas Inlet Pipe
Gas Valve
9. Use a Phillips screwdriver to remove the two screws at
location A - the connection below the gas valve where it
connects to the pipe. See Figure 4 for reference. Once the
screws are removed, carefully separate the pipe from the
gas valve.
10. Once the gas inlet pipe is detached from the gas valve, find
location B - the connection above the gas valve where it is
attached to the fan motor assembly. Carefully remove the
four screws by hand using a Phillips screwdriver and pull
the gas valve away from the fan assembly to access the gas
orifice.
Location B:
Remove 4 screws
here
Location A:
Remove 2 screws
here
Figure 4. Detaching Gas Valve from
Gas Inlet Pipe and Fan Motor Assembly
11. Once the Gas Orifice is exposed, remove the two screws
that hold the part in place. Remove the Gas Orifice from its
housing and prepare the new Gas Orifice for the LP
conversion for installation.
Remove two 2
screws here