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Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design Temperatures Two - Stage High Efficiency Furnace
Winter Design
Temperatures1 °F
(°C)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
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 figure22.
Vent Pipe
Diameter
PVC
2 in
21
3 in
12
2 in
11
3 in
n/a
2 in
6
3 in
n/a
Conditioned
Space
TABLE 7
Unit Input Size
040
PP
PVC
2
18
33
12
21
9
19
n/a
9
4
12
n/a
n/a
Conditioned
Space
Pipe Insulation
Unconditioned
Space
Figure 22
Page 19
060
PP
PVC
2
30
46
21
30
17
28
9
16
10
19
n/a
8
Exhaust
Pipe
Intake
Pipe
080
PP
2
42
30
25
16
16
8
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