Page 25
TABLE 7
Maximum Allowable Exhaust Vent Pipe Length (in ft.)
3
Without Insulation In Unconditioned Space For
Winter Design Temperatures Single - Stage High Eciency Furnace
Winter
Design
Temp
1
°F (°C)
Vent
Pipe
Diam
Unit Input Size
030
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 PVC
2
PP
1-1/2 in
N/A N/A
25 N/A 20 N/A N/A N/A N/A N/A
N/A N/A
2 in 18 16 31 28 50 48 30 30
2-1/2 in 13 N/A 24 N/A 42 N/A 56 N/A
3 in 9 9 18 18 35 35 47 47 42 42
20 to 1
(-7 to -17)
1-1/2 IN 15 N/A 20 N/A N/A N/A N/A N/A
N/A N/A
2 in 9 8 18 16 32 29 30 30
2-1/2 in 5 N/A 13 N/A 24 N/A 34 N/A
3 in 1
1
8 8 19 19 26 26 23 23
0 to -20
(-18 to -29)
1-1/2 in 10 N/A 15 N/A N/A N/A N/A N/A
N/A N/A
2 in 5
3
12 10 22 19 30 27
2-1/2 in 1
N/A
7 N/A 15 N/A 22 N/A
3 in N/A
N/A
2 2 10 10 16 16
13 13
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 ex-
ceed 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 gure31.
3 Vent length in the table is equivalent length. Each elbow is equivalent to 5ft of straight pipe and should be included when mea-
suring total length.
Conditioned
Space
Unconditioned
Space
Exhaust
Pipe
Intake
Pipe
Conditioned
Space
Pipe Insulation
Figure 31
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