Lennox SLP99UHV Series Unit Information page 54

General Guidelines for Vent Terminations
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the out-
doors. The SLP99UHV is classified as a direct vent, Cate-
gory IV gas furnace.
In Direct Vent applications, the vent termination is limited
by local building codes. In the absence of local codes, re-
fer to the current National Fuel Gas Code ANSI Z223-1/
NFPA 54 in U.S.A., and current CSA-B149 Natural Gas
and Propane Installation Codes in Canada for details.
Position termination according to location given in FIG-
URE 28. In addition, position termination so it is free from
any obstructions and 12" above the average snow accu-
mulation.
At vent termination, care must be taken to maintain pro-
tective coatings over building materials (prolonged expo-
sure to exhaust condensate can destroy protective coat-
ings). It is recommended that the exhaust outlet not be
located within 6 feet (1.8m) of a condensing unit because
the condensate can damage the painted coating.
Maximum Allowable Vent Pipe Length (in ft.
Winter Design
Vent Pipe
Temperatures1
Diameter
°F (°C)
1-1/2 in.
32 to 21
2 in.
(0 to -6)
2-1/2 in
3 in.
1-1/2 in.
2 in.
20 to 1
(-7 to -17)
2-1/2 in.
3 in.
1-1/2 in.
2 in.
0 to -20
(-18 to -29)
2-1/2 in.
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.
3 Vent lengths in table are equivalent length. Consider each elbow as 5ft of linear length.
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 24 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. FIGURE 29.
For Winter Design Temperatures Modulating High Efficiency Furnace
070
PVC PP
2
N/A N/A
11 9
7 N/A
2 2
N/A N/A
3 1
1 N/A
1 1
N/A N/A
1 1
1 N/A
1 1
NOTE - See TABLE 25 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.
Do not use screens or perforated metal in exhaust or
intake terminations. Doing so will cause freeze-ups and
may block the terminations.
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).
TABLE 25
) Without Insulation In Unconditioned Space
3
Unit Input Size
090
PVC PP
2
N/A N/A
14 12
10 N/A
6 6
N/A N/A
6 4
1 N/A
1 1
N/A N/A
1 1
1 N/A
1 1
Page 54
IMPORTANT
IMPORTANT
110
PVC PP PVC
2
N/A N/A
18 15 N/A
12 N/A
8 8 13
N/A N/A
8 6 N/A
3 N/A
1 1
N/A N/A
2 1
N/A
1
N/A
N/A
135
PP
2
N/A
13
N/A
2 2
N/A