Lennox MERIT Series Installation Instructions Manual page 19

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