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General Guidelines for Vent Terminations
In Direct Vent applications, combustion air is taken from
outdoors and the flue gases are discharged to the outdoors.
The NF97UM is then classified as a direct vent, Category IV
gas furnace.
In 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 CSA-B149 Natural Gas and Propane
Installation Codes in Canada for details.
Position termination according to location given in Figure
34. In addition, position termination so it is free from any
obstructions 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 an outdoor AC unit because the condensate
can damage the painted coating.
NOTE: See Table 21 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) Armaflex
or equivalent. In extreme cold climate areas, 3/4" (19mm)
Armaflex or equivalent may be necessary. Insulation must
be protected from deterioration. Armaflex with UV protection
is permissable. Basements or other enclosed 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.
31-5000723 Rev. 0
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).
Page 41
IMPORTANT
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