Page 30
31-5000729 Rev. 0
Maximum Allowable Exhaust Vent Pipe Length
3
(in ft.) without Insulation in Unconditioned Space for Winter Design
Temperatures Single - Stage High Efficiency Furnace
Winter Design Temperatures
1
ºF (ºC)
Vent Pipe
Diameter
Unit Input Size
045
070
090
32 to 21
(0 to -6)
PVC
2
PP
PVC
2
PP
PVC
2
PP
1-1/2 in.
20
N/A
20
N/A
N/A
N/A
2 in.
18
16
31
28
50
48
2-1/2 in.
13
N/A
24
N/A
42
N/A
3 in.
9
9
18
18
35
35
20 to 1
(-7 to -17)
1-1/2 in.
15
N/A
20
N/A
N/A
N/A
2 in.
9
8
18
16
32
29
2-1/2 in.
5
N/A
13
N/A
24
N/A
3 in.
1
1
8
8
19
19
0 to -20
(-18 to -29)
1-1/2 in.
10
N/A
15
N/A
N/A
N/A
2 in.
5
3
12
10
22
19
2-1/2 in.
1
N/A
7
N/A
15
N/A
3 in.
N/A
N/A
2
2
10
10
1
Refer 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
3
Vent length in table is equivalent length. Each elbow is equivalent to 5ft of straight pipe and should be included when measuring
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 7A through Table 7D or Table 8A through Table
8B.
NOTE
- If insulation is required an unconditioned space, it must be located on the pipe closed to the furnace.
Table 12.
Conditioned
Space
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 27. Insulating Exhaust Pipe in an Unconditioned Space
