Lennox ML193UH030XE36B Installation Instructions Manual page 22

Maximum Allowable Exhaust Vent Pipe Length (in ft.) Without Insulation In Unconditioned Space For
Winter Design Temperatures Single - 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 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 FIGURE 31.
Vent Pipe
Diameter
030
PP
PVC 2
1-1/2"
2 in
2-1/2 in
3 in
1-1/2"
2 in
N/A N/A
2-1/2 in
3 in
1-1/2"
2 in
2-1/2 in
3 in
Conditioned
Space
TABLE 7
Unit Input Size
045
PP
PVC 2 PVC
25 N/A 20
18 16 31
13 N/A 24
9 9 18
15 N/A 20
9 8 18
5 N/A 13
1 1 8
10 N/A 15
5 3 12
1 N/A 7
N/A N/A 2
Conditioned
Space
Pipe Insulation
Unconditioned
Space
FIGURE 31
Page 22
070 090
PP PP
2 PVC 2
N/A N/A N/A
28 50 48
N/A 42 N/A
18 35 35
N/A N/A N/A
16 32 29
N/A 24 N/A
8 19 19
N/A N/A N/A
10 22 19
N/A 15 N/A
2 10 10
Exhaust
Pipe
Intake
Pipe
110
PP
PVC 2
N/A N/A
30 30
56 N/A
47 47
N/A N/A
30 30
34 N/A
26 26
N/A N/A
30 27
22 N/A
16 16