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Maximum Allowable Vent Pipe Length (in ft.)
Winter Design
Vent Pipe
Temperatures1
Diameter
°F (°C)
1-1/2 in.
32 to 21
2 in.
(0 to -6)
2-1/2 in
3 in.
1-1/2 in.
2 in.
20 to 1
(-7 to -17)
2-1/2 in.
3 in.
1-1/2 in.
2 in.
0 to -20
(-18 to -29)
2-1/2 in.
3 in.
1Refer 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.
3Vent lengths in table 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 8 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 FIGURE 27..
For Winter Design Temperatures Modulating High Efficiency Furnace
070
PVC
N/A
11
7
2
N/A
3
1
1
N/A
1
1
1
Conditioned
Space
TABLE 9
Without Insulation In Unconditioned Space
3
Unit Input Size
090
PP
PVC
2
N/A
N/A
9
14
N/A
10
2
6
N/A
N/A
1
6
N/A
1
1
1
N/A
N/A
1
1
N/A
1
1
1
Conditioned
Space
Pipe Insulation
Unconditioned
Space
FIGURE 27
Page 23
110
PP
PVC
2
N/A
N/A
12
18
N/A
12
6
8
N/A
N/A
4
8
N/A
3
1
1
N/A
N/A
1
2
N/A
1
1
N/A
Exhaust
Pipe
Intake
Pipe
PP
2
N/A
15
N/A
8
N/A
6
N/A
1
N/A
1
N/A
N/A
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