508093-01
Issue 2033
Page 34 of 59
Maximum Allowable Exhaust Vent Pipe Length
3
(in ft.) without Insulation in Unconditioned Space For Winter Design
Temperatures Single - Stage High Efficiency Furnace
Winter Design
Temperatures
1
ºF (ºC)
Vent Pipe
Diameter
Unit Input Size
030
045
070
090
110
135
32 to 21
(0 to -6)
PVC
2
PP
PVC
2
PP
PVC
2
PP
PVC
2
PP PVC
2
PP
PVC
2
PP
1-1/2 in.
N/A
N/A
25
N/A
20
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
18
16
18
16
31
28
50
48
30
30
N/A
N/A
2-1/2 in.
13
N/A
13
N/A
24
N/A
42
N/A
56
N/A
N/A
N/A
3 in.
9
9
9
9
18
18
35
35
47
47
52
52
20 to 1
(-7 to -17)
1-1/2 in.
N/A
N/A
15
N/A
20
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
9
8
9
8
18
16
32
29
30
30
N/A
N/A
2-1/2 in.
5
N/A
5
N/A
13
N/A
24
N/A
34
N/A
N/A
N/A
3 in.
N/A
N/A
N/A
N/A
8
8
19
19
26
26
30
30
0 to -20
(-18 to -29)
1-1/2 in.
N/A
N/A
10
N/A
15
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
5
3
5
3
12
10
22
19
30
27
N/A
N/A
2-1/2 in.
N/A
N/A
N/A
N/A
7
N/A
15
N/A
22
N/A
N/A
N/A
3 in.
N/A
N/A
N/A
N/A
N/A
N/A
10
10
16
16
18
18
1
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2
Poly-Propylene vent pipe (PP) by Duravent and Centrotherm
3
Vent length in table is equivalent length. Each elbow is equivalent to 5ft. of straight pipe and should be included when measuring
total length.
NOTE- Maximum uninsulated vent lengths listed may include the termination (vent pipe exterior to the structure ) and cannot exceed
5 linear feet or the maximum allowable intake or exhaust vent length listed in Table 11 through Table 13.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See Figure 29.
NOTE - Concentric terminations are the equivalent of 5’ and should be considered when measuring pipe length.
Table 14.
Conditioned
Space
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 29. Insulating Exhaust Pipe in an Unconditioned Space
