Page 28
31-5000726 Rev. 0
Maximum Allowable Exhaust Vent Lengths with Furnace Installed in a Closet or Basement Using Ventilated
Attic or Crawl Space for Intake Air in Feet
Standard Termination at Elevation 0 - 4500 ft
Number
of 90°
Elbows
Used
1-1/2" Pipe
2" Pipe
2-1/2" Pipe
3" Pipe
Model
Model
Model
Model
45
70
90 110 135 45
70
90 110 135 45
70
90 110 135 45
70
90 110 135
1
25
20
n/a n/a n/a
66
51
29
9
n/a
95
95
73
38
n/a
113 112
93
93
89
2
20
15
61
46
24
4
90
90
68
33
108 107 88
88
84
3
15
10
56
41
19
n/a
85
85
63
28
103 102 83
83
79
4
10
n/a
51
36
14
80
80
58
23
98
97
78
78
74
5
n/a
46
31
9
75
75
53
18
93
92
73
73
69
6
41
26
4
70
70
48
13
88
87
68
68
64
7
36
21
n/a
65
65
43
8
83
82
63
63
59
8
31
16
60
60
38
3
78
77
58
58
54
9
26
11
55
55
33
n/a
73
72
53
53
49
10
21
6
50
50
28
68
67
48
48
44
Standard Termination at Elevation 4500 - 10,000 ft
Number
of 90°
Elbows
Used
1-1/2" Pipe
2" Pipe
2-1/2" Pipe
3" Pipe
Model
Model
Model
Model
45
70
90 110 135 45
70
90 110 135 45
70
90 110 135 45
70
90 110 135
1
25
20
n/a n/a n/a
66
51
29
n/a n/a
95
95
73
38
n/a
113 112
93
93
89
2
20
15
61
46
24
90
90
68
33
108 107 88
88
84
3
15
10
56
41
19
85
85
63
28
103 102 83
83
79
4
10
n/a
51
36
14
80
80
58
23
98
97
78
78
74
5
n/a
46
31
9
75
75
53
18
93
92
73
73
69
6
41
26
4
70
70
48
13
88
87
68
68
64
7
36
21
n/a
65
65
43
8
83
82
63
63
59
8
31
16
60
60
38
3
78
77
58
58
54
9
26
11
55
55
33
n/a
73
72
53
53
49
10
21
6
50
50
28
68
67
48
48
44
* Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Both Intake and
Exhaust must be same pipe size.
* Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length
calculation.
Table 10C.