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Roof Terminated
Exhaust Pipe
Ventilation
Furnace
Louvers
(Crawl Space)
Coupling or
3 in. to 2 in.
Transition
(Field Provided)
* See Maximum Vent Lengths table
NOTE-The inlet and outlet air openings shall each have a
free area of at least one square inch per 4,000 Btu (645mm
per 1.17kW) per hour of the total input rating of all equipment
in the enclosure.
Figure 32. 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. This furnace 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.
This furnace 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
34 or Figure 35. 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 (1.8 m) of a condensing unit because
the condensate can damage the painted coating.
507768-05G / 31-5000655
Inlet Air
Minimum
12 in. (305mm)
above Crawl
Space Floor
*Intake Debris Screen Provided
2
NOTE: See Table 6A through Table 6B 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" (13 mm) Armaflex or equivalent. In
extreme cold climate areas, 3/4" (19 mm) Armaflex or
equivalent may be necessary. Insulation 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 applications.
NOTE: During
approximately 20° F (6.7° C), units with long runs of vent
pipe through unconditioned space, even when insulated,
may form ice in the exhaust termination that prevents the
unit from operating properly. Longer run times of at least 5
minutes will alleviate most icing problems. Also, a heating
cable may be installed on exhaust piping and termination
to prevent freeze-ups. Heating cable installation kits are
available. See unit specification sheets for part numbers.
Do not use screens or perforated metal in exhaust
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 (305
mm).
Issue 2223
extremely
cold
temperatures,
IMPORTANT
IMPORTANT
below
Page 25 of 56
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