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Maximum Allowable Exhaust Vent Pipe Length (in ft.) without Insulation in Unconditioned Space for Winter Design
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
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 6 or Table 7A through Table 7C.
NOTE - If insulation is required an unconditioned space, it must be located on the pipe closed to the furnace.
507962-01
ºF
1
Vent Pipe
Diameter
2 in.
2-1/2 in.
3 in.
2 in.
2-1/2 in.
3 in.
2 in.
2-1/2 in.
3 in.
Conditioned
Space
Figure 27. Insulating Exhaust Pipe in an Unconditioned Space
Temperatures
045
070
PVC
PP
PVC
2
21
18
33
16
N/A
26
12
12
21
11
9
19
7
N/A
14
N/A
N/A
9
6
4
12
N/A
N/A
7
N/A
N/A
N/A
Table 8.
Conditioned
Space
Pipe Insulation
Unconditioned
Space
Issue 1922
Unit Input Size
090
PP
PVC
PP
2
2
30
46
42
N/A
37
N/A
21
30
30
17
28
25
N/A
21
N/A
9
16
16
10
19
16
N/A
13
N/A
N/A
8
8
Exhaust
Pipe
Intake
Pipe
110
PVC
PP
2
30
30
36
N/A
29
29
27
24
20
N/A
14
14
18
15
12
N/A
7
7
Page 23 of 54
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