Lennox ML193DFE Series Unit Information page 28

General Guidelines for Vent Terminations
In Non-Direct Vent applications, combustion air is taken
from indoors and the flue gases are discharged to the out-
doors. The ML193DFE is then classified as a non-direct
vent, Category IV gas furnace.
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the out-
doors. The ML193DFE is then classified as a direct vent,
Category IV gas furnace.
In both Non-Direct Vent and Direct Vent applications, the
vent termination is limited by local building codes. In the
absence of local codes, refer to the current National Fuel
Gas Code ANSI Z223-1/NFPA 54 in U.S.A., and current
CSAB149 Natural Gas and Propane Installation Codes in
Canada for details.
Position termination according to location given in FIG-
URE 31 or FIGURE 32. In addition, position termination so
it is free from any obstructions and 12" above the average
snow accumulation. At vent termination, care must be tak-
en to maintain protective coatings over building materials
(prolonged exposure to exhaust condensate can destroy
protective coatings). It is recommended that the exhaust
outlet not be located within 6 feet (1.8m) of a condens-
ing unit because the condensate can damage the painted
coating.
Maximum Allowable Exhaust Vent Pipe Length (in ft.)3 Without Insulation In Unconditioned Space For
Winter Design Temperatures Single - Stage High Efficiency Furnace
Winter Design
Vent Pipe
Temperatures
1
Diameter
°F (°C)
1-1/2 in
32 to 21
2 in
(0 to -6)
2-1/2 in
3 in
1-1/2in.
20 to 1 2 in
(-7 to -17) 2-1/2 in
3 in
1-1/2 in
0 to -20 2 in
(-18 to -29) 2-1/2 in
3 in
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
1
Poly-Propylene vent pipe (PP) by Duravent and Centrotherm.
2
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 13 or 14 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 30..
TABLE 15
045
PP
PVC
2
25 N/A
18 16
13 N/A
9 9
15 N/A
9 8
5 N/A
N/A N/A
10 N/A
5 3
N/A N/A
N/A N/A
Page 28
NOTE - See TABLE 15 for maximum allowed exhaust pipe
length without insulation in unconditioned space during
winter design temperatures below 32°F (0°C). If required
exhaust pipe should be insulated with 1/2" (13mm) Ar-
maflex or equivalent. In extreme cold climate areas, 3/4"
(19mm) Armaflex or equivalent may be necessary. Insu-
lation must be protected from deterioration. Armaflex with
UV protection is permissable. Basements or other en-
closed areas that are not exposed to the outdoor ambient
temperature and are above 32 degrees F (0°C) are to be
considered conditioned spaces.
IMPORTANT
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze-ups and
may block the terminations.
IMPORTANT
For Canadian Installations Only:
In accordance to CSA International B149 installation
codes, the minimum allowed distance between the
combustion air intake inlet and the exhaust outlet
of other appliances shall not be less than 12 inches
(305mm).
Unit Input Size
070
PP
PVC
2
20 N/A
31 28
24 N/A
18 18
20 N/A
18 16
13 N/A
8 8
15 N/A
12 10
7 N/A
N/A N/A
090
PP
PVC
2
N/A N/A
50 48
42 N/A
35 35
N/A N/A
32 29
24 N/A
19 19
N/A N/A
22 19
15 N/A
10 10