Lennox MERIT Series Installation Instructions Manual page 18

Size intake and exhaust pipe length separately. Values in table are for Intake OR Exhaust, not combined total. Intake and Exhaust must be same 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.
Number 2" Pipe
Of 90°
Model
Elbows
045
Used
1 71
2 66
3 61
4 56
5 51
6 46
7 41
8 36
9 31
10 26
Number 2" Pipe
Of 90°
Model
Elbows
045
Used
1 71
2 66
3 61
4 56
5 51
6 46
7 41
8 36
9 31
10 26
Maximum Allowable Intake or Exhaust Vent Length
Standard Termination at Elevation 0 - 4500 ft
070 090 045
56 34 105
51 29 100
46 24 95
41 19 90
36 14 85
31 9 80
26 4 75
21 70
16 n/a 65
11 60
Standard Termination Elevation 4501 - 10,000 ft
070 090 045
56 34 105
51 29 100
46 24 95
41 19 90
36 14 85
31 9 80
26 4 75
21 70
16 n/a 65
11 60
TABLE 7
2-1/2" Pipe
Model
070 090
105 83
100 78
95 73
90 68
85 63
80 58
75 53
70 48
65 43
60 38
2-1/2" Pipe
Model
070 090
105 83
100 78
95 73
90 68
85 63
80 58
75 53
70 48
65 43
60 38
Page 18
3" Pipe
Model
110 045 070
48 128 127
43 123 122
38 118 117
33 113 112
28 108 107
23 101 102
18 98 97
13 93 92
8 88 87
3 83 82
3" Pipe
Model
110 045 070
48 128 127
43 123 122
38 118 117
33 113 112
28 108 107
23 103 102
18 98 97
13 93 92
8 87 87
5 83 82
090
108
103
98
93
88
83
78
73
68
63
090
108
103
98
93
88
83
78
73
68
63