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Maximum Allowable Exhaust Vent Length Using Ventilated Attic or Crawl Space for Intake Air in Feet
1-1/2" Pipe
Number of 90°
Capacity
Elbows Used
070
1
2
3
4
5
n/a
6
7
8
9
10
NOTE: Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length
calculation.
General Guidelines for Vent Terminations
In Non-Direct Vent applications, combustion air is taken
from indoors or ventilated attic or crawlspace and the flue
gases are discharged to the outdoors. The NF96DV is then
classified as a non-direct vent, Category IV gas furnace.
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the outdoors.
The NF96DV is then classified as a direct vent, Category
IV gas furnace.
In both Non-Direct Vent and Direct Vent applications, the
vent termination is limited by local building codes. In the
absence of local codes, refer to the current National Fuel
Gas Code ANSI Z223-1/NFPA 54 in U.S.A., and current
CSA-B149 Natural Gas and Propane Installation Codes in
Canada for details.
Position termination according to location given in Figure
22 or Figure 31. In addition, position termination so it is
free from any obstructions and 12" above the average
snow accumulation.
At vent termination, care must be taken to maintain
protective coatings over building materials (prolonged
exposure to exhaust condensate can destroy protective
coatings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of an outdoor AC unit because
the condensate can damage the painted coating.
31-5000727 Rev. 0
Standard Termination at Elevation 0 - 10,000 ft
2" Pipe
Capacity
090
110
070
41
36
31
26
21
n/a
n/a
16
11
6
1
n/a
2-1/2" Pipe
Capacity
090
110
070
24
85
19
80
14
75
9
70
4
65
n/a
60
55
50
n/a
45
40
Table 10C.
NOTE: See Table 11 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32°F (0°C). If required
exhaust pipe should be insulated with 1/2" (13mm)
Armaflex or equivalent. In extreme cold climate areas,
3/4" (19mm) Armaflex or equivalent may be necessary.
Insulation must be protected from deterioration. Armaflex
with UV protection is permissable. Basements or other
enclosed areas that are not exposed to the outdoor
ambient temperature and are above 32 degrees F (0°C)
are to be considered conditioned spaces.
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and may
block the terminations.
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet
of other appliances shall not be less than 12 inches
(305mm).
Page 27
3" Pipe
Capacity
090
110
070
63
28
102
58
23
97
53
18
92
48
13
87
43
8
82
38
3
77
33
72
28
67
n/a
23
62
18
57
IMPORTANT
IMPORTANT
090
110
83
83
78
78
73
73
68
68
63
63
58
58
53
53
48
48
43
43
38
38
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