Lennox MERIT Series Installation Instructions Manual page 19

Maximum Allowable Exhaust Vent Lengths With Furnace Installed in a Closet or Basement Using Ventilated
NOTE - Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent
length calculation.
2" Pipe
Number
Model
Of 90°
Elbows
045 070
1 71 56
2 66 51
3 61 46
4 56 41
5 51 36
6 46 31
7 41 26
8 36 21
9 31 16
10 26 11
2" Pipe
Number
Model
Of 90°
Elbows
045 070
1 71 56
2 66 51
3 61 46
4 56 41
5 51 36
6 46 31
7 41 26
8 36 21
9 31 16
10 26 11
Attic or Crawl Space For Intake Air in Feet
Standard Termination at Elevation 0 - 4500 ft
090 110 045
34 14 115
29 9 110
24 4 105
19 100
14 95
9 90
4 n/a 85
80
n/a 75
70
Standard Termination Elevation 4500 - 10,000 f
090 110 045
34 100
29 95
24 90
19 85
14 80
n/a
9 75
4 70
65
n/a 60
55
TABLE 8
2-1/2" Pipe
Model
070 090 110
100 78 43
95 73 38
90 68 33
85 63 28
80 58 23
75 53 18
70 48 13
65 43 8
60 38 3
55 33 n/a
2-1/2" Pipe
Model
070 090 110
100 78 43
95 73 38
90 68 33
85 63 28
80 58 23
75 53 18
70 48 13
65 43 8
60 38 3
55 33 n/a
Page 19
3" Pipe
Model
045 070 090
118 117 98
113 112 93
108 107 88
103 102 83
98 97 78
93 92 73
88 87 68
83 82 63
78 77 58
73 72 53
t
3" Pipe
Model
045 070 090
118 117 98
113 112 93
108 107 88
103 102 83
98 97 78
93 92 73
88 87 68
83 82 63
78 77 58
73 72 53
110
98
93
88
83
78
73
68
63
58
53
110
98
93
88
83
78
73
68
63
58
53