Navien NPE-180A Installation Manual page 30

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 water heater's heat exchanger. This situation could lead to
the freezing of the heat exchanger and malfunction of the water
heater.
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 water heater.
When installed in a manufactured home (mobile home), all
combustion air must be supplied from the outdoors as described
on page 28.
When using non-direct venting, maintain non-direct vent
clearances shown on page 31 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 water heater:
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 in
Coupling 2 in
30 Installing the Water Heater
Pipe 2 in
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:
Maximum
Input
(BTU/H)
NPE-150S
120,000
NPE-180A
150,000
NPE-180S
NPE-210A
180,000
NPE-210S
NPE-240A
199,900
NPE-240S
Outdoor Indoor make
make up air is up air is
provided, provided,
a minimum a minimum
free area of free area of
2 2
1 in per 4,000 1 in per 1,000
BTU/H BTU/H
2
30 in
2
120 in
10 in (W) x 3 in
11 in (W) x
(H) or 6 in
11 in (H)
round
2
40 in
2
150 in
10 in (W) x 4 in
1
12 / in (W) x
4
(H) or 7 in
1
12 / in (H)
4
round
2
45 in
2
180 in
10 in (W) x 5 in
1
13 / in (W) x
4
(H) or 8 in
1
13 / in (H)
4
round
2
50 in
2
199 in
10 in (W) x 5 in
1
14 / in (W) x
4
(H) or 8 in
1
14 / in (H)
4
round