Page 32
31-5000728 Rev. 0
Figure 29. Equipment in Confined Space
(Inlet Air from Ventilated Attic and Outlet Air to
Outside)
Figure 30. Equipment in Confined Space
(Inlet Air from Ventilated Crawl Space and Outlet Air
to Outside)
General Guidelines for Vent Terminations
In Non-Direct Vent applications, combustion air is taken
from indoors and the flue gases are discharged to the
outdoors. The NF96US 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 outdoors.
The NF96US 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
CSA-B149 Natural Gas and Propane Installation Codes in
Canada for details.
Position termination according to location given in Figure
32 or Figure 41. 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 a condensing unit because
the condensate can damage the painted coating.
NOTE:
See Table 11 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.
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).
IMPORTANT
NOTE
: The inlet and outlet air openings shall each have a
free area of at least one square inch per 4,000 Btu (645mm
2
per 1.17kW) per hour of the total input rating of all equipment
in the enclosure.
* See Maximum Vent Lengths table
Inlet Air Minimum
12” (305mm)
above attic floor
Ventilation Louvers
Roof
Terminated
Exhaust Pipe
*Intake Debris
Screen
(provided)
Furnace
NOTE
: The inlet and outlet air openings shall each have a
free area of at least one square inch per 4,000 Btu (645mm
2
per 1.17kW) per hour of the total input rating of all equipment
in the enclosure.
* See Maximum Vent Lengths table
Inlet Air
Minimum
12” (305mm)
above crawl
space floor
Ventilation
Louvers
(crawl
space)
Roof
Terminated
Exhaust Pipe
*Intake Debris Screen (provided)
Furnace
Coupling or 3”
to 2” Transition
(field provided)
