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Maximum Allowable Exhaust Vent Lengths with Furnace Installed in a Closet or Basement Using Ventilated Attic or Crawl
Number
1-1/2" Pipe
of 90°
Capacity
Elbows
045
070
Used
1
15
10
2
10
3
4
5
6
n/a
n/a
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.
507735-03
Space for Intake Air in Feet
Standard Termination at Elevation 0 − 10,000 ft.
2" Pipe
Capacity
090
110
045
070
61
46
56
41
51
36
46
31
41
26
n/a
n/a
36
21
31
16
26
11
21
n/a
16
Pipe size determined in table 7.
2"
2"
2"
2"
or
DO NOT transition
from smaller to larger
pipe in horizontal runs
of exhaust pipe.
* When transitioning up in pipe size, use the shortest length of 2" PVC pipe possible.
NOTE: Exhaust pipe and intake pipe must be the same diameter.
Figure 22. Typical Exhaust Pipe Connections
2-1/2" Pipe
Capacity
090
110
045
070
24
100
80
19
95
75
14
90
70
85
65
80
60
n/a
75
55
n/a
70
50
65
45
60
40
55
35
Table 8.
2"
3"
or
TRANSITION
*2"
DO NOT transition
from larger to smaller
pipe in horizontal runs
of exhaust pipe.
Issue 1933
3" Pipe
Capacity
090
110
045
070
43
127
127
38
122
122
33
117
117
28
112
112
23
107
107
n/a
18
102
102
13
97
97
92
92
n/a
87
87
82
82
NOTE: 1-1/2" Vent Pipe
Diameter Allowed Only
on 045/070 Units
1-1/2"
TRANSITION
*2"
INTAKE
EXHAUST
TOP VIEW
090
110
108
108
103
103
98
98
93
93
88
88
83
83
78
78
73
73
68
68
63
63
Page 17 of 53
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