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Maximum Allowable 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 - 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 23A or Table 23B.
NOTE - If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See Figure 33.
without Insulation in Unconditioned Space for Winter Design Temperatures
3
Modulating High Efficiency Furnace
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
Figure 25. Insulating Exhaust Pipe in an Unconditioned Space
070
090
PVC
PP
PVC
2
N/A
N/A
N/A
11
9
14
7
N/A
10
N/A
N/A
6
N/A
N/A
N/A
N/A
N/A
6
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Table 21.
Conditioned
Space
Pipe Insulation
Unconditioned
Space
Page 42
110
PP
PVC
PP
2
2
N/A
N/A
N/A
12
18
15
N/A
12
N/A
6
8
8
N/A
N/A
N/A
4
8
6
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Exhaust
Pipe
Intake
Pipe
135
PVC
PP
2
N/A
N/A
N/A
N/A
N/A
N/A
13
13
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
31-5000723 Rev. 0
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