Navien NCB-180 Installation & Operation Manual page 39

Non-Direct Venting (Single Pipe)
If, at any time, the installation location could experience negative
pressure, there is a possibility of back drafting cold air through the
boiler's heat exchanger. This situation could lead to the freezing of
the heat exchanger and malfunction of the boiler.
However, building codes in most jurisdictions disallow negative
pressures in residences. In a home with a well-balanced air supply,
the heat exchanger should not be in danger of freezing. Because
the cause of back drafting is not considered a manufacturing
problem, any freezing damage which occurs from back drafting
will not be covered by the Navien warranty. If there is any question
about the possibility of back drafting in the installation location,
use a direct venting system for the boiler.
When using non-direct venting, maintain non-direct vent
clearances shown on page 39 as required by ANSI Z21.10.3 and
the National Fuel Gas Code, ANSI Z223.1/NFPA 54, and CAN/
CSA B149.1 Natural Gas And Propane Installation Code.
To use non-direct venting for the boiler:
1. Insert the termination end cap into the intake air duct. Do not
glue the end cap, to allow for easy removal and cleaning of the
cap.
Vent Termination Cap 2"
Coupling 2"
Vent Pipe 2"
38 Venting the Boiler
2. Provide two openings to allow for circulation of combustion air
as specified by ANSI Z223.1/NFPA 54 or CAN/CGA B-149.1:
NCB-180
Maximum Input
150,000
(BTU/H)
Outdoor
make up air 40 in
is provided, a 10 in (W) x
minimum free 4 in (H) or
area of 1 in , per 3 in round
2
4,000 BTU/H
Indoor make up
150 in
air is provided,
12 1/ in (W)
a minimum free
x 12 1/ in
area of 1 in per
2
(H)
1,000 BTU/H
NCB-210 NCB-240
180,000 199,000
45 in 50 in
2 2 2
10 in (W) x 10 in (W) x
5 in (H) or 3 5 in (H) or
in round 3 in round
175 in 199 in
2 2
13 1/ in (W) 14 1/ in (W)
x 13 1/ in x 14 1/ in
(H) (H)
2