Lennox ML193UH Installation Instructions Manual page 23

Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design Temperatures Single - Stage High Efficiency Furnace
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.
NOTE - Maximum unisulated 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 figure32.
Vent Pipe
Diameter
045
PVC
2 in. 26
2-1/2 in. 18
3 in. 14
2 in 16
2-1/2 in. 12
3 in. 9
2 in. 10
2-1/2 in. 8
3 in. 4
Conditioned
Conditioned
Space
TABLE 7
Unit Input Size
070 090
PVC PVC
44
32
26
28
20
16
20
14
10
Space
Pipe Insulation
Unconditioned
Space
FIGURE 32
Page 23
110
PVC
44 24
50 58
38 55
40 24
30 44
26 32
30 24
20 32
16 26
Exhaust
Pipe
Intake
Pipe
135
PVC
N/A
N/A
60
N/A
N/A
40
N/A
N/A
30