Navien NHB Series Installation & Operation Manual page 111

Procedure:
1. Turn off both gas and water supply to the boiler.
2. Unfasten the 4 latches (2 at the top and 2 at the bottom)
to remove the front cover and gain access to the internal
components. See Figure 1 for illustration of the front cover
clamps.
Figure 1. NFB Series Front cover
3. Remove the front cover and place it in a safe location to
prevent accidental damage.
4. With the internal components exposed, locate the gas inlet
pipe and the gas valve, as shown in Figure 2.
Figure 2. NFB Series Internal Components
Gas Valve
Gas Inlet Pipe
5. Remove the clip at location A – the connection above the gas
valve where it connects to the gas valve outlet adapter. See
Figure 3 for reference.
6. Find location B - the connection above the gas valve where it is
attached to the fan motor assembly. Carefully remove the four
screws using a Phillips-head screwdriver and pull the gas valve
outlet adapter away from the fan assembly to access the Gas
Orifice.
Figure 3. Detaching the Gas Valve Outlet Adapter
from the Gas Valve and Fan Motor Assembly
7. Once the Gas Orifice is exposed, remove the four screws
that hold the part in place. Remove the Gas Orifice from its
housing and prepare the new Gas Orifice for the high altitude
conversion for installation.
Figure 4. Access to Gas Orifice in Fan Assembly
Location B: Remove
4 screws here
Location A: Remove
the clip here
Remove 4
screws here
Appendixes 111