507867-02
Page 20 of 55
Issue 1933
Table 6.
BG921-E
Maximum Allowable Exhaust Vent Length with Furnace Installed in a Closet or Basement Using
Ventilated Attic or Crawl Space for Intake in Feet
Standard Termination at Elevation 0 - 10,000 ft
Number of
90° Elbows
Used
1-1/2" Pipe
2" Pipe
2-1/2" Pipe
3" Pipe
Capacity
Capacity
Capacity
Capacity
030 /
045
070
090
110
030 /
045
070
090
110
030 /
045
070
090
110
030 /
045
070
090
110
1
20
15
n/a
n/a
66
51
29
9
95
80
48
23
112
112
93
93
2
15
10
61
46
24
4
90
75
43
18
107
107
88
88
3
10
n/a
56
41
19
n/a
85
70
38
13
102
102
83
83
4
n/a
51
36
14
80
65
33
8
97
97
78
78
5
46
31
9
75
60
28
3
92
92
73
73
6
41
26
4
70
55
23
n/a
87
87
68
68
7
36
21
n/a
65
50
18
82
82
63
63
8
31
16
60
45
13
77
77
58
58
9
26
11
55
40
8
72
72
53
53
NOTE
: Additional vent pipe and elbows used to terminate the vent pipe outside the structure must be included in the total vent length
calculation.
TYPICAL EXHAUST PIPE CONNECTIONS IN UPFLOW DIRECT OR
NON-DIRECT VENT APPLICATIONS
* When transitioning up in pipe size, use the shortest length of 2” PVC pipe possible.
** When transitioning down in pipe size, use at least 1 foot of 2" PVC pipe.
NOTE
: Exhaust pipe and intake pipe must be the same diameter.
2”
2”
2”
2”
or
2”
EXHAUST
Pipe size determined in Table 5
TRANSITION
3”
*2”
**2”
1-1/2”
or
TRANSITION
EXHAUST
EXHAUST
NOTE
: 1-1/2” Vent
Pipe Diameter Allowed
Only on 030/045/070
Units
6”
MINIMUM
.
DO NOT transition
from larger to smaller
pipe in horizontal runs
of
exhaust pipe
.
EXHAUST
DO NOT transition
from smaller to larger
pipe in horizontal runs
of
exhaust pipe
.
EXHAUST
Figure 25.
