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Maximum Allowable Exhaust Vent Pipe Length
Winter Design Temperatures
(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- 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 7A through Table 7C.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See Figure 27.
NOTE - Concentric terminations are the equivalent of 5ft. and should be considered when measuring pipe length.
Page 22 of 52
Conditioned
Space
Figure 27. Insulating Exhaust Pipe in an Unconditioned Space
(in ft.) without Insulation in Unconditioned Space for Winter Design
3
ºF
Vent Pipe
1
Diameter
1-1/2 in.
2 in.
2-1/2 in.
3 in.
1-1/2 in.
2 in.
2-1/2 in.
3 in.
1-1/2 in.
2 in.
2-1/2 in.
3 in.
Conditioned
Space
Pipe Insulation
Unconditioned
Space
Temperatures
045
070
PVC
PP
PVC
2
22
N/A
20
21
18
33
16
N/A
26
12
12
21
12
N/A
20
11
9
19
7
N/A
14
N/A
N/A
9
8
N/A
13
6
4
12
N/A
N/A
7
N/A
N/A
N/A
Table 8.
Issue 2327
Exhaust
Pipe
Intake
Pipe
Unit Input Size
090
PP
PVC
PP
2
2
N/A
N/A
N/A
30
46
42
N/A
37
N/A
21
30
30
N/A
N/A
N/A
17
28
25
N/A
21
N/A
9
16
16
N/A
N/A
N/A
10
19
16
N/A
13
N/A
N/A
8
8
110
PVC
PP
2
N/A
N/A
30
30
36
N/A
29
29
N/A
N/A
27
24
20
N/A
14
14
N/A
N/A
18
15
12
N/A
7
7
508391-01
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