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Maximum Allowable Exhaust Vent Pipe Length
Winter Design Temperatures1 ºF
(ºC)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
1
Poly-Propylene vent pipe (PP) by Duravent and Centrotherm
2
Vent length in table is equivalent length. Each elbow is equivalent to 5ft of straight pipe and should be included when measuring
3
total 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 5A through Table 5C or Table 6.
NOTE - If insulation is required an unconditioned space, it must be located on the pipe closed to the furnace. See Figure 33.
Page 26 of 60
(in ft.) without Insulation in Unconditioned Space for Winter Design
3
Vent Pipe
Diameter
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.
3 in.
N/A
1-1/2 in.
2 in.
2-1/2 in.
N/A
3 in.
N/A
Conditioned
Space
Figure 33. Insulating Exhaust Pipe in an Unconditioned Space
Temperatures
045
070
PP
PVC
PP
2
2
N/A
25
N/A
18
33
30
N/A
26
N/A
12
21
21
N/A
20
N/A
9
19
17
7
N/A
14
N/A
N/A
9
9
8
N/A
13
N/A
6
4
12
10
N/A
7
N/A
N/A
N/A
N/A
Table 6.
Conditioned
Space
Pipe Insulation
Unconditioned
Space
Issue 2332
Unit Input Size
090
110
PVC
PP
PVC
PP
2
2
N/A
N/A
N/A
N/A
46
42
30
30
37
N/A
36
N/A
30
30
29
29
N/A
N/A
N/A
N/A
28
25
27
24
21
N/A
20
N/A
16
16
14
14
N/A
N/A
N/A
N/A
19
16
18
15
13
N/A
12
N/A
8
8
7
7
Exhaust
Pipe
Intake
Pipe
135
PVC
PP
2
N/A
N/A
N/A
N/A
N/A
N/A
42
42
N/A
N/A
N/A
N/A
N/A
N/A
23
23
N/A
N/A
N/A
N/A
N/A
N/A
13
13
508404-01
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