Lennox SLP98DFV Installation Instructions Manual page 22

Maximum Allowable Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space
Winter Design
Vent Pipe
Temperatures1
Diameter
°F (°C)
2 in.
32 to 21
(0 to -6)
2-1/2 in
3 in.
2 in.
20 to 1
2-1/2 in.
(-7 to -17)
3 in.
2 in.
0 to -20
2-1/2 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 7 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 figure24.
For Winter Design Temperatures Modulating High Efficiency Furnace
070
PVC PP
2
11 9
7
N/A
N/A
Conditioned
Space
TABLE 8
Unit Input Size
090
PVC PP
2
14 12
10 N/A
6 6
6 4
N/A N/A
Conditioned
Space
Pipe Insulation
Unconditioned
Space
FIGURE 24
Page 22
110
PVC PP PVC
2
18 15
N/A
12 N/A
8 8 13
8 6
N/A
N/A N/A
Exhaust
Pipe
Intake
Pipe
135
PP
2
N/A
13
N/A