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Maximum Allowable Exhaust Vent Pipe Length (in ft.
Winter Design Temperatures Two - Stage High Efficiency Furnace
Winter Design
1
Temperatures
°F (°C)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
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 are 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 24 or 25 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 figure28.
Vent Pipe
Diameter
045
2
PVC
PP
1-1/2 in.
22
N/A
2 in.
21
18
2-1/2 in.
16
N/A
3 in.
12
12
1-1/2 in.
12
N/A
2 in
11
9
2-1/2 in.
7
N/A
3 in.
N/A
N/A
1-1/2 in.
8
N/A
2 in.
6
4
2-1/2 in.
N/A
N/A
3 in.
N/A
N/A
Conditioned
Conditioned
Space
FIGURE 28
TABLE 26
3
)Without Insulation In Unconditioned Space For
Unit Input Size
070
090
2
PVC
PP
PVC
25
N/A
N/A
33
30
46
26
N/A
37
21
21
30
20
N/A
N/A
19
17
28
14
N/A
21
9
9
16
13
N/A
N/A
12
10
19
7
N/A
13
N/A
N/A
8
Space
Pipe Insulation
Unconditioned
Space
Page 61
110
2
2
PP
PVC
PP
PVC
N/A
N/A
N/A
N/A
42
30
30
N/A
N/A
36
N/A
N/A
30
29
29
42
N/A
N/A
N/A
N/A
25
27
24
N/A
N/A
20
N/A
N/A
16
14
14
23
N/A
N/A
N/A
N/A
16
18
15
N/A
N/A
12
N/A
N/A
8
7
7
13
Exhaust
Pipe
Intake
Pipe
135
2
PP
N/A
N/A
N/A
42
N/A
N/A
N/A
23
N/A
N/A
N/A
13
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