Lennox ELITE Series Installation Instructions Manual page 25

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 7 or TABLE 8 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 FIGURE 33.
Vent Pipe
Diameter
045
PVC
2 in 21
2-1/2 in 16
3 in 12
2 in 11
2-1/2 in 7
3 in 2
2 in 6
2-1/2 in 1
3 in 1
Conditioned
Conditioned
Space
TABLE 9
Unit Input Size
070
PP PP
2 PVC 2
18 33 30
n/a 26 n/a
12 21 21
9 19 17
n/a 14 n/a
2 9 9
4 12 10
n/a 7 n/a
1 2 2
Space
Pipe Insulation
Unconditioned
Space
FIGURE 33
Page 25
090
PP
PVC 2 PVC
46 42 30
37 n/a 36
30 30 29
28 25 27
21 n/a 20
16 16 14
19 16 18
13 n/a 12
8 8 7
Exhaust
Pipe
Intake
Pipe
110
PP
2
30
n/a
29
24
n/a
14
15
n/a
7