Page 18
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 SLP98UHV 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 Natu-
ral Gas and Propane Installation Codes in Canada for de-
tails.
Position termination according to location given in figure
20. In addition, position termination so it is free from any ob-
structions and 12" above the average snow accumulation.
At vent termination, care must be taken 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 condensing unit because
the condensate can damage the painted coating.
NOTE
− See table 6 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) Arma-
flex or equivalent. In extreme cold climate areas, 3/4"
(19mm) Armaflex or equivalent may be necessary. Insula-
tion on outside runs of exhaust pipe must be painted or
wrapped to protect insulation from deterioration. Exhaust
pipe insulation may not be necessary in some specific ap-
plications.
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 6
Maximum Allowable Vent Pipe Length Without Insulation In Unconditioned Space For
Winter Design Temperatures Modulating High Efficiency Furnace
Winter Design
Temperatures
1
°F (°C)
Vent Pipe
Diameter
Unit Input Size
070
090
110
135
32 to 21
(
(0 to −6)
2 in.
8
14
14
n/a
2−1/2 in.
6
9
12
n/a
3 in.
4
6
8
12
20 to 1
(−7 to −17)
2 in
5
7
8
n/a
2−1/2 in.
4
5
6
n/a
3 in.
2
2
4
6
0 to −20
(−18 to −29)
2 in.
3
4
5
n/a
2−1/2 in.
2
2
3
n/a
3 in.
1
1
1
2
1
Refer to 99% Minimum Design Temperature table provided in the current edition of the ASHRAE Fundamentals Handbook.
NOTE − Maximum unisulated vent lengths listed cannot exceed the maximum allowable intake or exhaust vent length listed in table 5.
