Navien NFB-175H, Руководство по установке, Страница: 61 / 135

61 Venting for Combustion Air
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 62 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"
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)
Outdoor
make
up air is
provided, a
minimum
free area of
1 in
2
, per
4,000
BTU/H
Indoor
make
up air is
provided, a
minimum
free area of
1 in
2
, per
1,000
BTU/H
NFB-
200H 199,900
50 in
2
10 in (W) x
5 in (H) or
8 in
round
199 in
2
14
1
/
4
in
(W) x
14
1
/
4
in (H)
NFB-
175H 175,000
44 in
2
10 in (W) x
5 in (H) or
8 in
round
175 in
2
13
1
/
4
in
(W) x
13
1
/
4
in (H)