Page 47
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 SLP99DFV 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 29. 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.
NOTE -
See TABLE 26 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).
TABLE 26
Maximum Allowable Vent Pipe Length (in ft.)
3
Without Insulation In Unconditioned Space
For Winter Design Temperatures Modulating High Efficiency Furnace
Winter Design
Temperatures1
°F (°C)
Vent Pipe
Diameter
Unit Input Size
070
090
110
32 to 21
(0 to -6)
PVC
2
PP
PVC
2
PP
PVC
2
PP
1-1/2 in.
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
11
9
14
12
18
15
2-1/2 in
7
N/A
10
N/A
12
N/A
3 in.
2
2
6
6
8
8
20 to 1
(-7 to -17)
1-1/2 in.
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
3
1
6
4
8
6
2-1/2 in.
1
N/A
1
N/A
3
N/A
3 in.
1
1
1
1
1
1
0 to -20
(-18 to -29)
1-1/2 in.
N/A
N/A
N/A
N/A
N/A
N/A
2 in.
1
1
1
1
2
1
2-1/2 in.
1
N/A
1
N/A
1
N/A
3 in.
1
1
1
1
N/A
N/A
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.
3Vent 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 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..
