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Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design
Vent
Temp
°F (°C)
Pipe Diam
1
32 to 21
2 in
(0 to -6)
3 in
20 to 1
2 in
(-7 to -17)
3 in
0 to -20
2 in
(-18 to -29)
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.
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 5 or 6 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 figure32.
Winter Design Temperatures Single - Stage High Efficiency Furnace
040
PP
PVC
2
18
16
9
9
9
8
N/A
5
N/A
Conditioned
Space
Conditioned
Space
Figure 32
TABLE 7
Unit Input Size
060
PP
PVC
2
31
28
18
18
18
16
8
8
12
10
N/A
N/A
Pipe Insulation
Unconditioned
Space
Page 24
080
PP
PVC
2
PVC
50
48
30
35
35
47
32
29
30
19
19
26
22
19
30
10
10
16
Exhaust
Pipe
Intake
Pipe
100
PP
2
30
47
30
26
27
16
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