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Maximum Allowable Exhaust Vent Pipe Length
Winter Design
Temperatures
ºF (ºC)
1
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 5A through Table 5D or Table 6A through Table
6B.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See Figure 33.
NOTE - Concentric terminations are the equivalent of 5' and should be considered when measuring pipe length.
31-5000728 Rev. 0
(in ft.) without Insulation in Unconditioned Space For Winter Design
3
Temperatures Single - Stage High Efficiency Furnace
Vent Pipe
Diameter
PVC
1-1/2 in.
25
18
2 in.
13
2-1/2 in.
9
3 in.
1-1/2 in.
15
9
2 in.
5
2-1/2 in.
1
3 in.
1-1/2 in.
10
5
2 in.
1
2-1/2 in.
N/A
3 in.
Conditioned
Space
Figure 31. Insulating Exhaust Pipe in an Unconditioned Space
Unit Input Size
045
070
PP
PVC
2
N/A
20
16
31
N/A
24
9
18
N/A
20
8
18
N/A
13
8
1
N/A
15
12
3
7
N/A
2
N/A
Table 11.
Conditioned
Space
Pipe Insulation
Unconditioned
Space
Page 33
090
PP
PVC
PP
2
2
N/A
N/A
N/A
28
50
48
N/A
42
N/A
18
35
35
N/A
N/A
N/A
16
32
29
N/A
24
N/A
8
19
19
N/A
N/A
N/A
10
22
19
N/A
15
N/A
2
10
10
Exhaust
Pipe
Intake
Pipe
110
PVC
PP
2
N/A
N/A
30
30
56
N/A
47
47
N/A
N/A
30
30
34
N/A
26
26
N/A
N/A
30
27
22
N/A
16
16
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