Removing The Internal Air Filter - Navien NHB Series Installation & Operation Manual

Flexible Vent Systems (Polypropylene)
Only VERTICAL installations are allowed. Horizontal
Note
terminations are prohibited.
The use of proper adapters and supports are required
to fully complete the installation.
The following table lists the flexible vent models that are approved
for use with this appliance in addition to the maximum allowable
vent lengths for the desired vent system.
Model Type Vent Dia.
NFB-
3 in
301C/399C
Only the flexible vent models listed above are approved for use
with this appliance.
All flexible vent pipe must be installed VERTICALLY through the
roof. No horizontal terminations are permitted.
Use a 3 in snap fit coupler or the Duravent PolyPro® Single Wall
vent pipes to connect the Duravent PolyPro® Flex 3 in vent pipes
to the exhaust.
After installation, ensure that the vent system is tightly sealed at
the joints.
All installation using the flexible vent materials must be in
INDIRECT VENTING only.
Refer to the manufacturer's literature for detailed information
and guidelines.
Flexible PP
Duravent PolyPro Flex
50 ft

5.5 Removing the Internal Air Filter

The NFB boiler is equipped with an internal air filter to remove dust
and debris that accumulate inside the boiler. The dust and debris
accumulated inside the boiler should be removed from the internal
air filter every two years. Follow the instructions below to remove
and replace the internal air filter.
1. Unfasten the 4 latches (2 at the top, 2 at the bottom) to remove
the front cover and gain access the internal components.
2. Remove the five screws on the internal air filter using a Phillips-
head screwdriver.
Venting the Boiler 61