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Maximum Allowable Exhaust Vent Pipe Length (in ft.
Winter Design Temperatures Two - Stage High Efficiency Furnace
Winter Design
Temperatures1 °F (°C)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
1Refer 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. Consider each elbow as 5ft. of linear length.
NOTE - Concentric terminations are the equivalent of 5' and should be considered when measuring pipe 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 7 or TABLE 8 which ever is less.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See FIGURE 33.
Vent Pipe
Diameter
045
PVC
1-1/2 in
22
2 in
21
2-1/2 in
16
3 in
12
1-1/2 in
12
2 in
11
2-1/2 in
7
3 in
2
1-1/2 in
8
2 in
6
2-1/2 in
1
3 in
1
Conditioned
Conditioned
Space
TABLE 9
) Without Insulation In Unconditioned Space For
3
Unit Input Size
070
PP
PP
PVC
2
2
n/a
20
n/a
18
33
30
n/a
26
n/a
12
21
21
n/a
20
n/a
9
19
17
n/a
14
n/a
2
9
9
n/a
13
n/a
4
12
10
n/a
7
n/a
1
2
2
Space
Pipe Insulation
Unconditioned
Space
FIGURE 33
Page 25
090
PP
PVC
PVC
2
n/a
n/a
n/a
46
42
30
37
n/a
36
30
30
29
n/a
n/a
n/a
28
25
27
21
n/a
20
16
16
14
n/a
n/a
n/a
19
16
18
13
n/a
12
8
8
7
Exhaust
Pipe
Intake
Pipe
110
PP
2
n/a
30
n/a
29
n/a
24
n/a
14
n/a
15
n/a
7
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