Page 30
31-5000726 Rev. 0
Conditioned
Space
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 23. Insulating Exhaust Pipe in an Unconditioned Space
Maximum Allowable Exhaust Vent Pipe Length
3
(in ft.) without Insulation in Unconditioned Space for Winter Design
Temperatures
Winter Design
Temperatures
1
ºF
(ºC)
Vent Pipe
Diameter
Unit Input Size
045
070
090
110
135
32 to 21
(0 to -6)
PVC
2
PP
PVC
2
PP
PVC
2
PP
PVC
2
PP
PVC
2
PP
1-1/2 in.
22
N/A
25
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
21
18
33
30
46
42
30
30
N/A
N/A
2-1/2 in.
16
N/A
26
N/A
37
N/A
36
N/A
N/A
N/A
3 in.
12
12
21
21
30
30
29
29
42
42
20 to 1
(-7 to -17)
1-1/2 in.
12
N/A
20
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
11
9
19
17
28
25
27
24
N/A
N/A
2-1/2 in.
7
N/A
14
N/A
21
N/A
20
N/A
N/A
N/A
3 in.
N/A
N/A
9
9
16
16
14
14
23
23
0 to -20
(-18 to -29)
1-1/2 in.
8
N/A
13
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
6
4
12
10
19
16
18
15
N/A
N/A
2-1/2 in.
N/A
N/A
7
N/A
13
N/A
12
N/A
N/A
N/A
3 in.
N/A
N/A
N/A
N/A
8
8
7
7
13
13
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 10A through Table 10C.
NOTE
- If insulation is required in an unconditioned space, it must be located on the pipe closest to the furnace. See Figure 23.
Table 11.
