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TABLE 18
Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a Closet or Basement Using Ventilated
Attic or Crawl Space For Intake Air in Feet
NOTE - 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.
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the
total vent length calculation
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
045 070 090 110 135 045 070 090 110 135 045 070 090 110 135 045 070 090 110 135
1
20 15
n/a n/a n/a
71
56 34 14
n/a
100 100 78 43
n/a
118
117
98 98 94
2
15 10
66
51
29
9
95
95 73 38
113
112
93 93 89
3
10
n/a
61
46 24
4
90
90 68 33
108 107 88 88 84
4
n/a
56 41
19
n/a
85
85 63 28
103 102 83 83
79
5
51 36 14
80
80 58 23
98
97
78 78 74
6
46 31
9
75
75 53 18
93
92
73 73
69
7
41
26
4
70
70 48 13
88
87
68 68 64
8
36
21
n/a
65
65 43
8
83
82
63 63 59
9
31
16
60
60 38
3
78
77
58 58 54
10
26 11
55
55 33 n/a
73
72
53 53 49
Standard Termination Elevation 4500 - 10,000 ft
Number
Of 90°
Elbows
Usedl
1-1/2” Pipe
2” Pipe
2-1/2” Pipe
3” Pipe
Model
Model
Model
Model
045 070 090 110 135 045 070 090 110 135 045 070 090 110 135 045 070 090 110 135
1
20 15
n/a n/a n/a
71
56 34
n/a n/a
100 100 78 43
n/a
118
117
98 98 94
2
15 10
66
51
29
95
95 73 38
113
112
93 93 89
3
10
n/a
61
46 24
90
90 68 33
108 107 88 88 84
4
n/a
56 41
19
85
85 63 28
103 102 83 83
79
5
51 36 14
80
80 58 23
98
97
78 78 74
6
46 31
9
75
75 53 18
93
92
73 73
69
7
41
26
4
70
70 48 13
88
87
68 68 64
8
36
21
n/a
65
65 43
8
83
82
63 63 59
9
31
16
60
60 38
3
78
77
58 58 54
10
26 11
55
55 33 n/a
73
72
53 53 49