Lennox SLP98UHV Installation Instructions Manual page 19

Maximum Allowable Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design
1
Temperatures °F (°C)
32 to 21
(0 to -6)
20 to 1
(-7 to -17)
0 to -20
(-18 to -29)
1
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
2
Poly-Propylene vent pipe (PP)
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 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 figure21.
Winter Design Temperatures Modulating High Efficiency Furnace
Vent Pipe
Diameter
PVC
2 in. 8
2-1/2 in. 6
3 in. 4
2 in 5
2-1/2 in. 4
3 in. 2
2 in. 3
2-1/2 in. 2
3 in. 1
Conditioned
Space
TABLE 6
Unit Input Size
070 090
2 2
PP PVC
8 14 13
N/A 9 N/A
3 6
5 7
N/A 5 N/A
2 2
3 4
N/A 2 N/A
1 1
Conditioned
Space
Pipe Insulation
Unconditioned
Space
FIGURE 21
Page 19
110
2
PP PVC PP
16 15
12 N/A
5 8 7
6 8 7
6 N/A
2 4 3
4 5 4
3 N/A
1 1 1
Exhaust
Pipe
Intake
Pipe
135
2
PVC PP
N/A N/A
N/A N/A
12 11
N/A N/A
N/A N/A
6 5
N/A N/A
N/A N/A
2 1